Seaworthy, watertight, floatable container for an offshore wind turbine maintenance program

ABSTRACT

A container for maintenance capsule as a component of a maintenance system for an offshore wind turbine maintenance program. The container transports tools, parts and maintenance personnel to and from respective wind turbine towers. The container is seaworthy, watertight and floatable, and can be loaded on a maintenance vessel which carries the container to and from a wind turbine tower.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.14/775,456 filed Sep. 11, 2015, which is a National Stage application ofInternational Application No. PCT/US2014/024634, filed on Mar. 12, 2014,which claims priority of U.S. Provisional Application No. 61/793,822,filed on Mar. 15, 2013, all of which are incorporated herein byreference in their entireties.

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates to the maintenance of wind turbines mounted ontowers located in bodies of water, and in particular to containers andcapsules for transporting workmen or maintenance personnel, tools andparts to and from such wind turbines.

Description of the Prior Art

Wind turbines are currently being used or expected to be used offshorein wind farms. Wind farms are essentially multiple wind turbinesdisposed in the same locale for generating large amounts of electricpower. There are presently thousands of wind farms in a number ofcountries throughout the world producing about 200 gigawatts ofelectrical energy, and this number is expected to increase tremendouslyover the coming decade as low cost oil supplies are depleted and fear ofnuclear power increases due to accidents. In China alone where airpollution due to coal-fired power plants is affecting vast areas, theyexpect over the years to produce near 750 gigawatts of electrical energyfrom wind farms. Many wind farms are offshore since there are lessobstructions to the wind than on land, so that the average wind speed isconsiderably higher over open water. However, offshore wind farms aremore expensive to build than are wind farms on land, and the maintenancecosts are relatively higher, particularly in salt water, since the saltwater and sea spray are corrosive towards most of the components of windturbines. Most wind farms that are offshore have wind turbines describedas fixed-bottom turbines, that is, having their support towers foundedon the sea floor. More recently, floating wind turbines anchored to thesea floor in even deeper water have been constructed. Power istransmitted from offshore turbines by means of undersea cables.

Amongst the conditions which have to be accounted for in an offshorewind farm are waves. Waves are generally under 2.5 m, and the averageshould be considered to be 3 m. However, high wave conditions occuroccasionally, and the maximum survival waves have been determined to be9.7 m. Currently, for safety reasons, wind turbine maintenance shouldcurrently generally not be attempted when the swell conditions exceed1.5 m.

There are number of maintenance systems currently employed for windfarms. One is the step transfer system. In this system, a vessel sailsfrom a port and conducts operations and maintenance on the respectivewind turbines as required. Personnel step off the vessel onto a ladderon the tower holding the wind turbine and attach themselves to a slidingsafety harness between the two vertical poles of the ladder and thenclimb upwards as required. The maximum wave height is usually 1.5 m forsafe transfer using the step transfer system. The step transfer systemis widely used, and relatively simple and cost effective. However, thereare safety implications, and it can be difficult to perform theoperations and maintenance required during periods when there are highcurrents or wave heights above 1.5 m. The occurrence of periods of highwaves could delay access and prevent departure increasing the total timeto perform the operations and maintenance, and trapping the limitednumber of maintenance personnel on board the wind turbine towerapparatus, rendering the step transfer system inefficient. It is desiredthat turbine wind towers should be accessible about 95% of the time, butit has been found that the step transfer system is operable about 75% ofthe time in the summer and below 45% of the time in the winter. It hasbeen judged that the step transfer system is unlikely to be the bestmethod for use in many wind farms.

Another system involves the use of lifts and cranes, and this ispresently the industry standard for transferring tools and equipment tothe workmen on offshore turbines. Lifts and cranes are used to transferequipment, but rarely personnel, all in relatively good weather.

Another system is called the “Waterbridge,” which is an inflatablebridge attached to a vessel and presented to a wind turbine through theattachment of a cable to the foundation of the wind turbine. The cableis kept taut with a constant tension winch. The object of the technologyis to absorb the vessel motions through passive use of the inflatablebridge, and the vessel would have the same motion as it would if it wereat anchor. In use, a vessel approaches the foundation of the windturbine, and a cable is hooked over a set of upward curved “Rhino Horns”on a transition piece. The cable is tensioned and the vessel retreatsfrom the wind turbine. An inflatable bridge is then winched up the cableto make positive contact with a ladder on the turbine tower. Personnelare then transferred across the bridge to the ladder. The Waterbridge iscost effective in that it can be deployed when necessary from a vesseland only one platform is needed for all turbines. It can be retrofittedto an existing access boat. A fall arrest lanyard is required for safetypurposes. However, only limited field tests have been performed with theWaterbridge. Another shortcoming is that transfer in marginal wave swellconditions may be difficult because the Waterbridge is fixed at theturbine, and it will still be moving up and down significantly at theboat end, because it only uses passive damping of the waves.

The Ampelmann is a stand-alone offshore access system. The Ampelmannmust be used with a large vessel. It is quite sophisticated using areverse flight simulator to compensate for the motion of the wavesbeneath the boat. The Ampelmann has been used in the oil and gas sector.It can be used on any vessel which is more than 50 m in length and canbe used by a small crew. It does not require dynamic positioning oradjustments to the vessel. However, it is very expensive and may not becost effective. It is also quite complicated, having complex movingparts requiring high maintenance. Another problem is the possibleleakage from the hydraulics.

The Momac Offshore Transfer System 500 (“MOTS 500”) is aself-stabilizing system for providing safe access to offshore structuresby actively compensating for motions of the vessel, rather than passivecompensation through hydraulics and damping. MOTS 500 uses provenrobotics technology and real-time motion measurement equipment. It canbe installed on small and fast vessels, and can be used on existingtransfer structures without modification. It has been found to be safe,even in the case of power breakdown or other failures, and requires lowmaintenance and has a seaworthy construction. The problem with MOTS 500is that is has not been previously tested in an offshore wind project.It cannot be retrofitted to an existing vessel and it must be able tocarry a minimum of three tons at the stern/bow.

An Offshore Access System/Offshore Transfer System (“OAS/OTS”) isessentially a combination of the Waterbridge and the Ampelmann. TheOAS/OTS is a passive bridge extending from the boat to a turbine, and isanchored against the turbine in the same way as is the Waterbridge, andis deployed in a manner similar to that of the Ampelmann. It iseffective in that it is secured to the ladder at the turbine tower, andit allows greater time to secure fall arrest lanyards at the latter.However, the OAS/OTS is bulky, requiring a large vessel. It only offersa small improvement over existing practices for significant waveheights. The transition piece would probably require severalmodifications. It has not been used in offshore wind turbines, and couldbe very costly.

The Small Waterplane Area Twin Hull (“SWATH”) is another possible meansfor maintaining wind turbines. This system uses a special type ofcatamaran which is a very stable vessel. The previously described steptransfer system can take place with a catamaran or a specially designedplatform for installation on a catamaran vessel when personnel are to betransferred to the turbine. SWATH has been used for a number of years inthe North Sea, and could be used with a deployable Reinforced InflatableBoat (“RIB”). Furthermore, the catamaran would reduce the incidence ofseasickness. However, a catamaran does have a large draft of about 3 mwhich would limit its shallow water operation. Furthermore, the proposedcatamaran would be 29 m long, which is quite long and would increase theoperating expense of the system.

Another possible system for maintenance of offshore wind turbines isSafe Offshore Access (“SASH”, a Swedish acronym). SASH is docking systemwherein personnel boarding a fixed structure can step onto it by takingonly one step from one horizontal plane to another. This procedureminimizes the time when the boarding personnel are exposed or vulnerableto risk. The boat is an integrated part of the system and facilitatesthe transfer to the fixed structure because of its raised platform. Thesystem itself has several raised platforms, for stepping onto a raisedplatform of the wind turbine tower. The boat can move 180.degree. aroundthe docking point between the boat and the tower. The complete SASHsystem has two diagonally mounted piles per wind turbine so that theboat can always meet the sea bow on. The bow and fender of the boat makeit possible to use the boat's engine to control the friction needed tokeep the boat stable in terms of the rolling and vertical movements. Theboarding personnel do not need to jump or climb, but are able to walkfrom one fixed structure to another without stress and without any timepressure. This is a fast and improving method. However, since there isonly a single hinge point between the pressure point, this magnifies thegap between platform and vessel during high sea states which may renderthis system unsafe. Also, the SASH system may not be applicable to allfoundation types. It is not adapted for tides, which would seem to benecessary. It is currently only used on a Swedish lighthouse andrequires a high level of skill of the vessel's skipper.

A Sliding Ladder (“SLILAD”) is a turbine mounted passive system fromMomac GmbH & Co. KG, a German company that produced the MOTS 500discussed earlier. In operation, the SLILAD is fixed to the vessel sothat there is no relative movement when the personnel step across theladder. Once the personnel are securely on the SLILAD, it becomes fixedto the platform and the personnel are able to climb up it if there is norelative movement between the SLILAD and the platform. Since SLILAD hasautomatic tide level adjustment, there will be no growth of mussels orvegetation on the used part of the latter. The SLILAD has a simple andseaworthy construction, and it is easy to use. However, Momac is nolonger developing the SLILAD so it may not be hereafter commerciallyavailable. There is an expense involved in maintaining SLILAD and thereis a risk of damage due to the large number of moving parts.

Helicopter transfer is well-known. A heli-hoist pad is installed on eachwind turbine. Personnel and equipment are winched down one at a time. Amaximum of five technicians can be transferred using a helicopter.Helicopters are expensive, and although they can be operated with manykinds of sea-state, they certainly would be dangerous in inclementweather or if the wind turbine is operating. Helicopter transfer isfast, but expensive and the number of personnel and amount of equipmentthat can be carried per trip is limited. There are risks, health andsafety concerns. Helicopters have higher maintenance requirements, arerelatively energy inefficient, and are limited in operative range.

Another possible system is the Personnel Transfer System (“PTS”) whichis a crane and winch system which is only being developed at this time.It is operated remotely and involves a vessel with fuzzy logic control.It can transfer one load of equipment and one person to the turbine.There have not been any instances of this technology being utilized,although there is at least in one study in which it has been considered.Among its strengths are that there is no risk associated with climbingthe transition piece ladder as the PTS lifts. The PTS could beretrofitted to existing vessels, and there is no mechanical contactbetween the vessel and the turbine. However, amongst its weaknesses isthat only one person could be transferred at a time, rendering it slowand involving significant waiting times for persons waiting transfer.Also, a person would not feel safe when suspended several meters abovethe sea being only supported by a harness, so that survival suits wouldbe necessary. More importantly, this type of maintenance system is onlyin its preliminary stage, and it is not ready for operation.

A recent development is the Houlder's Turbine Access System (“HTAS”). Itis essentially a passive damping mechanism similar to the OAS/OTSdiscussed earlier, but on a smaller scale which could be fitted to smallvessels. It has a unique tuned damping system to reduce the vesselsmotion response at the bow, but does not attempt to maintain the bowstationary relative to the tower. An access ramp is heave and rollcompensated to provide a constant transfer position relative to thetower, either by way of a ladder or platform depending on the towerconfiguration. The HTAS has been shown to provide for safe transfer atwave heights of 2 m without any relative movement between the accessramp and platform position. Amongst its advantages are that it wouldrequire small adjustment to existing procedures and vessel designs, thatit is relatively inexpensive and may be economically more favourablethan the previously described SWATH and other systems. However, the onlyincrease is the safe access for swell heights exceeding by 0.5 m from1.5 m to 2 m, but it comes from a company without sufficient reputationor experience, and would require a lot of testing.

A new proposal for maintaining offshore wind turbines is a wavedeflection harbour. The purpose of this device is to eliminate wavesentirely. It would fit over a transition piece and be attached to abearing which rotates freely around the position piece according to thedirection of the current. When a boat approaches, the deflection harbourwould be able to lock into position by use of a remote control operatedbraking mechanism, similar to that used to stop turbine blades on somewind farms. The wave deflection harbour is a pair of walls which areflat and meet at a point, with the separated walls being connected by acurved wall. The proposed design moves the stagnation point back furtherinto incoming water so that the water will attempt to reattach furtherfrom the transition piece, and when it does, it would actually help thevessel into the local harbour. The free rotation of the wave deflectionharbour assures that it will be in the correct position for desired flowconditions to occur. The biggest design constraint is the force that isexerted on the foundations. Amongst its advantages are that it couldsave costs in the long run, that it could increase the size of allowablesea swells and could be applied in many wind farms. However, while thewave deflection harbour is still at its design stage, it may not be costeffective, it would add to capital expenditures, it would require moretime through research, testing and prototyping, it may not be operablewith some foundation types and the waves may come from a differentdirection than the current, and could have an adverse effect on thelocal sea state conditions.

An offshore wind farm maintenance vessel has been prepared by OffshoreShip Designers, an Anglo-Dutch company. It is intended to improveoptions of deep water wind turbines, reduce maintenance costs and carbonemissions. A mother ship remains in offshore deep water wind farms andhas a number of catamaran workboats which carry wind turbine engineersto service the wind turbines. It is a submersible dock ship intended toaccompany the foregoing engineers, as well as a crew, service personnel,ships and a support crew. It is further intended to remain offshorerather than reporting to port, and workboats are deployed from the dockship. It is intended that the fast catamaran and monohull workboats goout from shore to wind farms closer to shore, but not for deep waterwind farms. The dock ship is also intended to support Autonomous Rescueand Recovery Craft which are safe watercraft and can support marine andhelicopter operations remote from the mother ship in emergency or rescueoperations, limited only by their rough weather capabilities. Thelargest mother ship is intended to accommodate up to 200 engineers andwould have extensive recreational, catering facilities and a wastehandling plant. A support vessel is intended to carry twenty five windturbine engineers and carry fuel, potable water, dry and refrigeratedstorage containers. It is supposed to have a crane, a walkway and twodaughter workboats. This concept appears to be very extensive.

A container is disclosed in U.S. Patent Publication No. 2009/0242581(Heitkoetter). However, Heitkoetter discloses a container which is usedfor holding dense materials and which can be locked to prevent an enddoor from swinging open rapidly due to the weight of the material orpressure of the material inside the container (Par. [0034]). The sidesare angled to facilitate dumping of the material from the container whenthe end door is opened (Par. [0035]). The container of Heitkoetter iswatertight, and does have vents for allowing gases to leave thecontainer but prevent anything from entering the container (Par.[0039]). There is nothing in the publication indicating that thecontainer of Heitkoetter is floatable. Nothing in Heitkoetter suggeststhat it is floatable when filled with dense materials or that it can beused for transporting personnel and tools for repairing a wind turbineor anything else.

European Patent Publication No. 0 053 770 (MacDonell et al.) discloses acarrier which is adapted to be moved between a first platform and asecond platform in the off-shore oil industry. For example, it can bemoved from a water vessel to a platform located above the water. It thenwould have to be moved from the platform to the vessel, all during thepossible occurrence of high waves. The carrier is described forpersonnel transfer to carry as many as thirty people. The carrier is notdescribed as being seaworthy meaning capable of voyaging safely upon thesea, watertight or floatable. Chinese Patent Application No. 202186506(U) discloses a lift diving site-seeing chamber having a glass chamberand a camera through which a person, who could be a tourist, can viewthe exterior of the diving sightseeing cabin. There is every indicationthat this diving cabin is meant to sink, in diving it is only supportedby a cable or cables run over pulleys affixed to the top of the divingsightseeing cabin, and it could not be used to carry personnel and toolsfor repairing an offshore wind turbine or any other type of such unit.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a seaworthycontainer for use with a system for maintaining offshore wind turbines.

Another object of the present invention is to provide a seaworthycontainer for use with a maintenance system for maintaining windturbines in a wind farm.

A more specific object of the present invention is to provide seaworthycontainer for use with a maintenance system for wind turbine towerapparatus used in offshore wind farms for carrying maintenancepersonnel, tools and parts to and from a wind turbine tower.

It is a further object of the present invention to provide a seaworthycontainer for a maintenance system for maintaining offshore windturbines, which container can be quickly and safely transferred betweena maintenance vessel and a wind turbine tower apparatus, regardless ofthe weather or sea conditions.

A further object of the present invention is to provide a seaworthy,watertight, floatable container for a wind turbine maintenance systemfor maintaining offshore wind turbine tower apparatuses.

It is also an object of the present invention to provide a seaworthycontainer that can be transported by a launch/recovery (“L/R”) cradlefor the purposes of being launched from, received by, moved by andstored on a maintenance vessel.

It is yet additional object of the present invention to provide acontainer which is watertight, and can hold up to five and possibly morerepair persons along with the necessary tools and parts for removing andreplacing the defective or worn parts on the respective wind turbines ordiagnose and restart them, for a wind turbine maintenance system asdescribed above.

It is yet another object of the present invention to provide a seaworthymaintenance capsule holding a container which is buoyant in case themaintenance capsule should fall into the surrounding sea, both toprotect any repair personnel on board and the parts and equipmentcarried therein and to propel itself away if necessary from collidingwith the wind turbine tower when it is deposited in the sea, for amaintenance system for wind turbine tower apparatus.

It still a further object of the present invention to provide amaintenance capsule as described above that is capable of holding up tofive repair persons and possibly more, and a ton or more of equipment.

A general object of the present invention is to provide a seaworthycontainer for all-weather maintenance system for offshore wind turbinetower apparatus, which container is safe, efficient and effective inoperation, and which can be constructed and used economically.

These and other objects will be apparent to those skilled in the artfrom the description to follow and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective, partially cut-away, schematic view of amaintenance capsule according to a preferred embodiment of theinvention.

FIG. 1A is a detailed cross sectional, schematic view of the upper partof the maintenance capsule shown in FIG. 1.

FIG. 2 is a partial, schematic, perspective view of a preferredembodiment of a crane assembly which is shown on a portion of a windturbine tower apparatus transporting a maintenance capsule to or from amaintenance vessel, according to a preferred embodiment of theinvention.

FIG. 3 shows a partial cross sectional, perspective view of the craneassembly on a wind turbine tower apparatus as shown in FIG. 2.

FIG. 4 shows a partial cross sectional, schematic view of a trolley on atruss extending from an offshore wind turbine tower raising amaintenance capsule according to a preferred embodiment of theinvention. FIG. 4A is a partial view of a body member assembly attachedto a gimbal ring, which is in turn connected to a lower ring-likemember. FIGS. 4B and 4C are alternate ways for attaching wheels formoving the trolley along the crane assembly. FIG. 4D is a detailexploded view of part of a latching assembly incorporated in thetrolley.

FIG. 5 is a perspective, schematic view of the lower part of a trolleytransporting a maintenance capsule according to a preferred embodimentof the invention.

FIG. 6 is a partial, schematic, cross sectional view of a dampingmechanism portion of a gimbal latching assembly according to a preferredembodiment of the invention.

FIG. 7 is a schematic, perspective, partially cut-away view of amaintenance vessel according to a preferred embodiment of the invention.FIG. 7A shows an alternative path to that shown in FIG. 7.

FIG. 8 is a detailed, partial, partially cut-away schematic view of themaintenance vessel illustrated in FIG. 7 showing components fortransferring maintenance capsules thereon.

FIG. 9 is a schematic partially cut-away perspective view of alaunch/recovery (“L/R”) cradle according to a preferred embodiment ofthe invention.

FIG. 9A is a perspective schematic view of the base of the L/R cradleshown in FIG. 9, revealing a drive assembly.

FIGS. 9B, 9C, 9D and 9E are schematic top, bottom, side and endelevations of a gear drive assembly for the L/R cradle shown in FIG. 9.

FIG. 9F is a top elevation of an alternate gear drive assembly from thatshown in FIG. 9B.

FIG. 9G is a cross sectional schematic view of the deck of a maintenancevessel showing slots in which an L/R cradle is transported on the deck.

FIG. 9H is a schematic perspective view of an idler assembly for use inthe L/R cradle shown in FIG. 9, and FIG. 9I is across sectionalschematic view showing a slot in the deck of the maintenance vesselaccording to an embodiment of the invention showing the idler assemblyof FIG. 9H therein.

FIG. 10 is a schematic perspective view showing a detail of the stern ofthe maintenance vessel shown in FIG. 8.

FIG. 11 is a schematic, perspective view of an elevator and shockabsorbing apparatus used on the stern of the vessel as shown in FIG. 10.

FIG. 12 is a detailed cross sectional, schematic view of a part of theUR cradle located on a deck part of the maintenance vessel shown in FIG.7, and a maintenance capsule cooperating with the L/R cradle.

FIG. 13 is a top cross sectional detail of door arrangements in thestern part of the maintenance vessel according to the preferredembodiment of the invention in schematic form, and

FIG. 14 shows an alternate door arrangement shown in FIG. 13.

FIG. 15 is a detailed, side cross sectional view of the stern part ofthe maintenance vessel shown in FIG. 7.

FIG. 16 is a schematic, perspective view of the lower portion of aturbine tower incorporating aspects of the preferred embodiment of theinvention showing a maintenance vessel transferring a maintenancecapsule to the turbine tower and for lifting a wheeled equipment box upthe tower.

FIG. 17 is a perspective view of a flexible services carrier and aportion of a trolley according to an embodiment of the invention, andFIG. 17A is a schematic end view of a trolley, a crane boom and a rigidservices carrier.

FIG. 18 is a perspective view of a flexible services carrier in a craneboom which supports a trolley, and FIG. 19 is a perspective view of aflexible services carrier in a crane boom.

FIGS. 20 and 20A are partial perspective and partial side views of arack chain drive for a modular carrier or flexible services carrieraccording to an aspect of the invention.

FIG. 21 is a schematic, perspective view of the upper portion of theturbine tower shown in FIG. 16.

FIG. 22 is an enlarged view of a portion of the maintenance tower shownin FIGS. 16, 21 and 27 with aspects of the preferred embodiment of theinvention incorporated therein.

FIG. 23 is an enlarged, cross-sectional view of a nacelle on top of aturbine tower with various aspects of the preferred embodiment of theinvention shown therein, and FIG. 23A is a partial, cutaway side view ofa cargo elevator carrying a storage box.

FIG. 24 is a side cross-sectional view of an extra-tall storage box on apartially shown cargo elevator.

FIGS. 25, 25A, 25B and 25C are perspective, schematic views showingportions of a rack drive chain used with the preferred embodiment of theinvention.

FIGS. 26 and 26A are schematic, cross-sectional and perspective views ofthe rack drive chain shown in FIG. 20 and how it is used in thepreferred embodiment of the present invention.

FIG. 27 is a perspective view of a drive chain segment, and FIGS.27A-27D are detailed views of a drive chain segment as shown in FIGS.20-20B and 27.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention in its preferred form includes as its basiccomponents a maintenance capsule with a container which would carry agroup of repair personnel and their equipment for maintaining anoffshore wind turbine on a wind turbine tower and for returning repairpersonnel and equipment to a maintenance vessel such as a ship or boat.The equipment comprises tools and replacement parts. The maintenancecapsule and the container are conveyed from and to a wind turbine towerapparatus by means of such a maintenance vessel. The maintenance vesselwould carry a number of maintenance capsules configured as required andthey would each be transferred to a wind turbine tower apparatus bymeans of an appropriate crane apparatus or assembly which is also partof the invention, which is located at the wind turbine tower apparatus.The maintenance capsule and the container must be as strong or strongerthan shipboard escape vehicles or pods of the type that are dropped fromthe stern of a ship from considerable heights into the sea (any body ofwater is referred to herein as the sea). The container preferably has acylindrical shape with truncated upper and bottom portions. As explainedearlier, the maintenance capsule in its preferred form is able to carryfive persons or possibly more plus the necessary equipment. The termcapsule includes the container and other auxiliary items. In some cases,the capsule and container are one and the same.

In calm conditions, the maintenance capsule is transferred to and from amaintenance vessel and a wind turbine tower apparatus by means of awinch aboard a trolley disposed on a crane assembly on the wind turbinetower apparatus. In moderately severe conditions, deployment to the windturbine is achieved by connecting a strong floating rope from thetrolley to be collected by the maintenance vessel, locked into areceptacle atop the maintenance capsule which is pulled off the saidvessel. Retrieval by the vessel is done by a strong floating ropedeployed from the bottom of the capsule which is captured by themaintenance vessel and pulled by a winch on the vessel onto alaunch/recovery cradle on the vessel. In the case of the most severeweather, deployment to the wind turbine is achieved in the same manneras moderately severe conditions, except that the maintenance vesselstands off as the maintenance capsule is dragged off into the sea andthen upwards. Recovery under the most severe conditions is achieved whenthe maintenance capsule is dropped in the sea, and a miniatureradio-homing boat transports a strong line therefrom to the maintenancevessel, whereupon a strong floating rope is pulled out of the capsule bythe use of said line and then captured by the vessel for pulling thecapsule up a raisable recovery ramp in the vessel. Maintenance capsulesare stored and transported on and within the vessel on launch/recoverycradles.

Referring to FIG. 1, a maintenance capsule 10 is shown in schematic formin an upright position. Capsule 10 includes a seaworthy, watertight,floatable container 11 having various walls and other external andinternal structures. A rope, cable or other capsule attachment linedischarge port 12 is located in a first end 13 at the top of maintenancecapsule 10 for holding a floatable rope, releasable cable or othercapsule attachment line as discussed below. A series of seats or otherperson support structure 14 (only one is shown) shaped to holdmaintenance personnel during transport of maintenance capsule 10 areincluded, it being preferred that there are up to five or possibly moresuch seats 14 for persons as required. Each seat 14 preferably includesappropriate shock absorber 15 shown schematically. Maintenance capsule10 further has a watertight bulkhead 16 separating a personnelcompartment 18 in which seats 14 are located, from a storage or cargocompartment 20 in which tools and parts and other equipment shown in astorage box 22 for a wind turbine are stored and appropriatelyrestrained. Access from personnel compartment 18 to cargo compartment 20is by way of a hatch assembly 24 in bulkhead 16.

Hatch assembly 24 includes a hatch cover 26 as is common in seagoingvessels. Personnel compartment 18 further has an access door 30 goingthrough a generally cylindrical outside outer wall 32, forming theoutside of personnel compartment 18 and cargo compartment 20. Door 30interfaces with the exterior of capsule 10. Personnel compartment 18 mayhave a window 34 in door 30, as well as a series of windows 36 in therest of personnel compartment 18. A cargo compartment access door 28through which storage box 22 can be moved is provided. Doors 28 and 30,and windows 34 and 36 are all watertight, as is the rest of maintenancecapsule 10 to render it seaworthy. As explained below, the weightdistribution of maintenance capsule 10 is such that when it is disposedin the sea, it floats with a longitudinal axis 98 near horizontal.

Another watertight bulkhead 38 forms a ceiling for personnel compartment18, for defining a second compartment 39. A truncated conical outershell 40 extends between the top of outer wall 32 to a shoulder 42. Atruncated wall 44 has a wider diameter than is the diameter at the upperend of outer shell 40, for defining shoulder 42 and concludes at capsuleattachment line discharge port 12. As explained later, shoulder 42 issymmetrical about longitudinal axis 98, and can be latched to the lowerpart of a trolley 124 (FIG. 2) on a boom of a crane on a wind turbinetower apparatus 100 having a wind turbine 101 positioned on a windturbine tower 102. A recess portion 46 in a nose portion 60 of capsule10 is provided to define rope or cable receiving and discharge port 12.

A rope, cable or other capsule attachment line 48 is received by acapsule attachment line holding-and-releasing apparatus 50 including areceptacle 51 suitably radiused at the entry to avoid cutting orfatiguing said rope or capsule attachment line 48, in a capsuleattachment line engaging apparatus forming part of said capsule line, inthe form of a barb 52 and fixed on said capsule attachment line 48 bysome appropriate means such as swaging. Barb 52 and capsule attachmentline 48 are releasably held in recess portion 46 by a holding mechanism54, shown in enlarged form in FIG. 1A. Barb 52 has an annular depression55 for receiving the nose of at least one ratchet 56 mounted on a pivot58 fixed in nose portion 60 of maintenance capsule 10. The diameters ofa head portion 66 and a tail portion 57 of barb 52 are the same, so thatthe longitudinal axis of barb 52 will be closely aligned with thelongitudinal axis of recess portion 46. An internal structure may berequired in some instances so that barb 52 can swivel relative tocapsule attachment line 48 to avoid undue twisting of said line 48.Ratchet 56 is loaded by a spring 64 to the latched position, meaningthat ratchet 56 engages head portion 66 of barb 52 and releasably holdsbarb 52 and capsule attachment line 48 fixed in recess portion 46 ofnose portion 60 of maintenance capsule 10. Various ratchet controlapparatuses can be used for selectively releasing barb 52 from recessportion 46. Barb 52 may also incorporate a floatation compartment orbody sufficient to allow barb 52 to float on the sea. The one employedas shown in FIG. 1A is a hydraulic or pneumatic piston assembly 68. Whenit is decided to unlatch barb 52 and capsule attachment line 48 fromrecess portion 46, hydraulic piston assembly 68 is activated by someappropriate means such as an electro-mechanical actuator (not shown),and a piston rod 70 is driven forward to rotate ratchet 56counterclockwise, with enough force to overcome the load imposed byspring 64 plus frictional and other loads. The rotation of ratchet 56about pivot 58 releases barb 52. Capsule attachment lineholding-and-releasing apparatus 50 includes each of said receptacle 51,barb 52, holding mechanism 54, ratchet 56, pivot 58, spring 64, pistonassembly 68 and piston 70.

Returning to FIG. 1, a truncated shell or operational compartment outerwalls in the form of a truncated conical outer wall 72 forms an outsideof capsule operational compartment 74 of maintenance capsule 10.Truncated annular wall 72 has a groove 398 near a lower end 73 ofmaintenance capsule 10. A watertight bulkhead 76 is disposed across thetop of operational compartment 74 to separate the latter from cargocompartment 20. Disposed inside of operational compartment 74 isoperational equipment 75 including a towrope storage compartment 78 inwhich a tow line in the form of a towrope 80 is coiled and attached tomaintenance capsule 10 by a lug or attachment point 81 on towrope 80.Towrope 80 has at its other end a connecting loop or other form oftermination to which a light line 82 is secured, and by which towrope 80can be collected and attached to a winch drum or cable aboard themaintenance vessel so that towrope 80 may be wound onto said winch drum.Spool of light line 82 may be stored on board a miniature radio-homingboat 84 if towrope 80 is too stiff or heavy to be easily otherwisedispensed. Towrope 80 can be composed of woven wires (i.e. a cable orwire rope), plastic or other fibers or a combination thereof, fibers orany other material capable of withstanding the forces, stresses andstrains to which towrope 80 is expected to endure. Light line 82 issecured to and stored on a dispensing spool within miniatureradio-homing boat 84 located in a miniature radio-homing launch tube 86.Miniature radio-homing boat 84 may directly take out towrope 80, iftowrope 80 is sufficiently light and strong, and permit its collectionby a maintenance vessel 300 as described hereinafter. Operationalequipment 75 further includes the foregoing miniature radio-homing boatlaunch tube 86.

Maintenance capsule 10 has a series of air vents 88 for enabling capsule10 to vent air from operational compartment 74 as required. In order toprovide capsule 10 with means to steer it when capsule 10 is in the sea,an electric water jet thruster 90 with an electric motor 92 constitutinga component of operational equipment 75, may be provided and which ispowered by a battery 93. Electric water jet thruster 90 is composed of asteerable nozzle 94 that is able to move in the directions indicated byarrows 96 to direct capsule 10 in a desired direction. Also encompassedin operational equipment 75 are electric water jet thruster 90, electricmotor 92 and battery 93. It should be understood that a non-electricwater jet thruster could also be used.

The approximate size for maintenance capsule 10 for the details asdiscussed below would have an approximate height L.sub.c of up to 6 mand approximate diameter D.sub.c of up to 3 m. The approximate weight ofmaintenance capsule 10 holding five work persons, tools and parts couldbe as much as five tons. As noted previously, maintenance capsule 10should be able to withstand being dropped from a considerable height ina manner similar to modern life boats which are dropped from the sternof a ship. The size could vary according to operating conditionsaccording, for example, to the conditions of the sea in the area of theturbine, the weather conditions, the number of workers to betransported, the amount and weight of tools and parts, etc.

The construction of maintenance capsule 10 is such as to protect theon-board personnel and equipment from harsh external conditions as mayoccur in the area of the wind farm. In view of the harsh conditionswhich could occur, it is intended that maintenance capsule 10 could haveenough supplies and equipment to enable personnel to survive in themaintenance capsule for two or three days without external assistance.

Aspects of wind tower turbine apparatus 100 are shown in schematic formin FIGS. 2 and 3. Referring to FIG. 2, a maintenance capsule 10 is shownbeing lifted in the direction indicated by arrows 109 and 111 fromvessel 300 disposed in the sea. Vessel 300 has an upper surface or deck303, a capsule support apparatus in the form of a launch/recovery(“L/R”) cradle 302 in a capsule support-apparatus holding bay or anupper or cradle-holding bay 304 at the stern or rear of vessel 300.Upper bay 304 is disposed below upper surface 303.

Wind turbine tower 102 extends from the floor of the sea via a number ofpossible foundations. Wind turbine tower 102 includes turbine vanes 103(one of which is shown), which rotate in the direction shown by an arrow105. A long, swivelable crane assembly 104 is mounted on tower 102 andheld there in part by a structured assembly 106 forming part of craneassembly 104. If the sea currents flow in one direction only as shown byarrows 107, the swivelling capability may be dispensed with allowing fora much smaller, lighter crane, and the fixed crane would be directeddownstream.

Crane assembly 104 further includes a boom in the form of a preferablylightweight truss 108 (although a tubular construction with an internalweatherproof access way could be beneficial), a swing-and-supportassembly 133 in the form of a tower-engaging support 110 which itselfincludes a lower annular support ring or rail 112 surrounding andengaging tower 102, an upper annular support ring or rail 114, astructural assembly 116 connecting lower annular support ring 112 andtruss 108, and vertical support structures 118 and 120 extendingrespectively from tower-engaging support 110 to upper annular supportring 114. A counterweight assembly 122 extends from lower annularsupport ring 112 in the opposite direction from truss 108. Trolley 124depends from truss 108 and is movable along the underside of truss 108.Assembly 133 also includes an upper annular rail 154 (FIG. 3) discussedbelow.

A walkway or access platform or service platform 126 surrounds tower102. A safety fence 128 forms a guard rail around walkway 126, andsupport flanges 130 support walkway 126.

Swivelable crane assembly 104 is able to swing around wind turbine tower102 in order to both withdraw capsules 10 from maintenance vessels 300when maintenance is to be performed on tower 102, and to depositcapsules 10 in vessels 300 following maintenance, and maintenance vessel300 is preferably positioned downstream of the wind turbine tower 102.As shown in detail in FIG. 3, wind turbine tower 102 is a hollowstructure having a longitudinal axis 132. In order to accomplish theannular rotation of crane assembly 104 about wind turbine tower 102, alower annular ring rail 134 which extends outwardly from tower 102 andis integral therewith. Lower annular ring rail 134 is composed of anupper annular disk-like portion 138 opposite to a lower annulardisk-like portion 136. A lower annular vertical member or upstandingportion 140 extends between portions 136 and 138 distal from tower 102.A few annular upwardly-facing recesses 141 defined by a few lowerhorizontal flanges 142 extend toward tower 102 from lower annularsupport ring 112 with which it is integral. A pair of annular verticalupstanding walls 143 extends upwardly from each flange 142 to definerecesses 141. Recesses 141 are integral with lower support ring 112 oftower-engaging support 110 below disk-like portion 136, and each has atleast two radially-extending axles 144, preferably equiangularlydisposed about the centerline of crane assembly 104, which extend acrossand into walls 143 defining each recess 141 to resist lifting forces ontower-engaging support 110 due to the upwardly traveling capsule 10impacting trolley 124. Each axle 144 carries a rotatable anti-frictionroller 146. Only a few rollers and axles are needed, and two would be anappropriate number of rollers. A lower, annular, inwardly-facing recess148 (open towards wind turbine tower 102), defined by opposing radialwalls 149 extending inwardly from lower annular support ring 112 withwhich it is integral, preferably has equiangularly-spaced vertical axles150. Axles 150 extend through opposite horizontal walls 149 defining theheight of recess 148, on which are disposed rotatable anti-frictionrollers 152.

Upper annular support rail 154 extends from wind turbine tower 102 in aposition above and opposite to lower annular support rail 134. Upperannular support rail 154 has a lower disk-like portion 156 and an upperdisk-like portion 158 whose ends distal from tower 102 are connected byan upper annular vertical member or upstanding portion 160. Uppersupport ring 114 of tower-engaging support 110 has a pair of verticalwalls 163 and 165 defining an annular, downwardly facing recess 161.Extending through walls 163 and 165 defining recess 161 are a series ofradially extending, preferably equiangularly spaced, axles 162 on whichare disposed vertically oriented rollers 164. Another inwardly facing,annular recess 166 faces lower annular ring 154 and has extendingbetween a pair of horizontal walls 167 and 169 defining recess 166, aset of vertically oriented axles 168, which are preferably equiangularlyspaced, for holding a set of horizontal anti-friction rollers 170.Rollers 164 and 170 rotate around upper annular rail 154 in the samemanner that rollers 146 and 152 engage lower annular rail 134 tofacilitate the relatively low friction rotation of swivelable craneassembly 104 about wind turbine tower 102.

As noted, counterweight assembly 122 extends from lower annular supportring 112. As shown in FIG. 3, counterweight assembly 122 is connected tolower annular support ring 112 by means of an arm 172. A yoke 174extends outwardly from lower annular support ring 112, and an axle 176extends through yoke 174 and arm 172. Lower annular support ring 112 isconnected to upper annular support ring 114 by vertical supportstructure 120, and yoke 174 is part of structure 120. Likewise, anotherarm 178, located above arm 172, extends from a yoke 180 which isattached to or part of upper annular support ring 114. Yoke 180 is alsointegral with structure 120. An axle 182 extends through arm 178 andyoke 180. Arms 172 and 178, and their respective yokes 174 and 180 areconnected to counterweight 122 as partly indicated in FIG. 3 in apivotable construction, so that counterweight 122 is able to pivot withrespect to axles 176 and 182 and may not exert bending moments into arms172 and 178. A pair of sheet metal or plastic weather covers 184 and 186extend outwardly as sheet metal flanges from wind turbine tower 102 andupper annular support ring 114 in an overlapping fashion to preventwater from getting into the spacing between wind turbine tower 102 andupper annular support ring 114.

Rollers 146, 152, 164 and 170 are preferably made from suitable alloysof cast iron or steel. All of the vertical forces applied to upperannular support ring 114 are resisted by rollers 146 and 164, and by thesurfaces of annular ring or lower annular rail 134 and upper annularrail 154.

As noted earlier, structural assembly 116 extends between lightweighttruss 108 and upper annular support ring 114. With further reference toFIG. 3, structural assembly 116 is pivotably attached to upper annularsupport ring 114 by means of an axle 188 extending through a yoke 190(which is integral with ring 114) and through a hole in an end ofstructural assembly 116 to avoid inducing bending moments in eitherparts connected together. A similar arrangement (not shown) is providedfor attaching a lower structural assembly or connecting lugs 192 tolightweight truss 108 to also enable the movement of structural assembly116 and lugs 192 with respect to swivelable crane assembly 104.

Referring next to FIGS. 4 and 4A, trolley 124 is shown mounted on truss108. Truss 108 has wheel support structure shown as horizontal upper andlower support flanges 193 which extend either outwardly or inwardly fromboth sides of webs 194 of truss 108. Trolley 124 includes a movementstructure 198 having a number of axles 200 rotatably supported in axleholders 202 on which are mounted rotatably held wheels 204 for engagingand riding on flange 193. Wheels 204 are located on the upper portion ofmovement structure 198, and a support member or support-and-holdingassembly 222 cooperates with the lower portion of movement structure 198as discussed below. Support member 222 includes an annular L-shapedportion 208. Support member 222 is connected to a rotationalbearing-and-drive device 205 via L-shaped annular support 208.Rotational bearing-and-drive device 205 comprises a rotational bearingassembly 206 and two other ring-like members, namely a gimbal ring 214and the other lower ring-like member 216. (Wheels 204 could have otherstructural arrangements with a modified web 194. Referring to FIG. 4B,alternate wheels 204′ are mounted on opposing axles 200′ extending froma support member 222′ (which is modified from support member 222). Web194′ is configured to provide a track 223′ for each of wheels 204′ sothat trolley 124 can move along web 194′, as well as to coordinate themovement of support member 222′ along web 194′. Another possiblemodification is shown in FIG. 4C. Wheels 204″ are mounted on axles 200″extending from modified support member 222″. Web 194″ has been modifiedto include a track 223″ for receiving and allowing the rotation ofwheels 204″ to enable the movement of trolley 124 along web 194″.Rotational bearing assembly 206 is composed in part of ball or otherbearings 210 for reducing friction between support member 222 and bodymember assembly 212. Body member assembly 212 is thus connected tomovement structure 198. Body member assembly 212 has at its upperportion an inverted recessed annular structure 218 having an upperflange 220 for cooperating with annular L-shaped portion 208 and ball orother bearings 210 to control the rotation of rotationalbearing-and-drive device 205, including the rotation of gimbal ring 214.

Support member 222 rides along with movement structure 198 by virtue ofthe travel of wheels 204. Body member assembly 212 also includes acapsule line-holding apparatus in the form of a winch 224 (which couldbe attached higher on rotational bearing-and-drive device 205 than isshown or configured as in tower cranes for winding capsule attachmentline 48 extending from maintenance capsule 10 thereon). Lower ring-likemember 216 comprises a driven tensioning guide roller mechanism 226 andincludes a set of pairs of driven tensioning guide rollers 228 and 230.The latter are provided to tension capsule attachment line 48 extendingbetween winch 224 and tensioning guide roller mechanism 226 whichmaintains the capsule attachment line 48 under tension to preventbacklash. A set of dampers 232 are provided for damping movement betweengimbal ring 214 and, thus, inverted recessed annular structure 218 andlower ring-like member 216. A further set of guide rollers 237 guide themovement of capsule attachment line 48 between guide rollers 228 and230. Lower ring-like member 216 is gimballed and has a damper assembly231 and a latching assembly 235. Damper assembly 231 includes dampers232 and 234, which are also shown in FIG. 5 and discussed in furtherdetail below. Latching assembly 235 includes in part unlatching armactuating assemblies 246 for releasing capsule 10 when required. Dampers232 and 234 damp the movement of body member assembly 212, particularlywhen maintenance capsule 10 is suspended by capsule attachment line 48and is attached to lower ring-like member 216 as described below.

Latching assembly 235 further includes a set of three or four latchingmechanisms 236 which are provided on lower ring-like member 216. Eachlatching mechanism 236 includes a latching device in the form of alatching arm 238 with engagement ends 240 for engaging maintenancecapsule 10 just beneath shoulder 42, a spring support arm 242, a spring244 and unlatching device in the form of the foregoing unlatching armactuating assembly 246 for opening each latching mechanism 236 or otherforms.

Referring to FIG. 4D, actuating assembly 246 is shown as a hydraulicactuator or hydraulic actuating assembly 248 having inlet and outletlines 250 and 252, and a piston 254 having a forked head 256 forengaging latching arm 238 to open respective latching arms 238 fromtheir latched positions. Thus, spring 244 biases each latching mechanism236 to its latching condition, and latching arm 238 can cause eachlatching mechanism 236 to assume its releasing condition.

Turning next to FIG. 5, lower ring-like member 216 is shown in furtherdetail. As noted previously, the lower part of lower ring-like member216 includes damped latching assembly 235. Inverted recessed annularstructure 218 is pivoted by means of arms 258 which extend outwardly andradially from gimbal ring 214. Lower ring-like member 216 has twoupstanding arms 262 (FIG. 4A) and as explained above, dampers 232interconnect lower ring-like member 216 and recessed annular structure218. Dampers 234 interconnect inverted recessed annular structure 218and gimbal ring 214.

Dampers 232 are shown in further detail in FIG. 6. Each damper 232 ispivotally supported in damper supporting mounts 264 mounted in a support265 and has a piston 266 mounted for movement through a seal 271integral with piston 266, vertically as shown by arrows 267 in ahydraulic cylinder 268 which holds hydraulic fluid 270. Hydraulic fluid270 is part of a hydraulic system 272 whose flow is controlled by a flowrestrictor 274 and a bypass valve 277, flow restrictor 274, and ahydraulic pressure relief valve 276. Flow restrictor 274, pressurerelief valve 276 and bypass valve 277 collectively form damping circuitcomponents 281. A small powered hydraulic system 278 is in parallel withsaid damping circuit components 281 and is alternatively selectable byuse of a valving apparatus shown as two-way valves 280.

The purpose of damper assembly 231 is to damp the motion of maintenancecapsule 10 when it is fastened to trolley 124 by latching assembly 235.When capsule 10 is initially suspended on capsule attachment line 48,flow restrictor 274 is bypassed by bypass 277 to allow capsule 10 toswing freely as shown by arrows 279. Then, bypass 276 is closed and flowrestrictor 274, with integral over-pressure relief, damps the motion.Small powered hydraulic system 278 (or springs for accomplishing thiseffect) may be then selected and used to make the longitudinal axis ofcapsule 10 vertical if the damping system and/or wind pressure hasstopped capsule 10 in a non-vertical attitude.

Referring to FIG. 4, movement structure 198 is shown with its axles 200supported in axle holders 202 on which wheels 204 are mounted.Rotational bearing-and-drive device 205 which includes gimbal ring 214and lower ring-like member 216, comprises driven tensioning guide rollermechanism 226, body member assembly 212 which comprises invertedrecessed annular structure 218 and capsule line-holding apparatus (suchas winch 224), dampers 232 and 234 which damp the motion of latchingassembly 235, actuating assembly 246, arms 258 and hydraulic system 272.

Maintenance vessel 300 is shown in FIGS. 7, 8, 10 and 13-15. Referringto FIG. 7, vessel 300 preferably has a length L.sub.v of about 100meters, a width W.sub.v of about 12 meters and a height H.sub.v of about12 meters, although different dimensions may be used for stability orother reasons. The main purpose of maintenance vessel 300 is totransport preconfigured maintenance capsules 10 and maintenancepersonnel to and from a wind turbine farm and to deploy and recover themaintenance personnel and their equipment within the maintenance capsule10 as may be required. Maintenance vessel 300 would be capable ofapproaching the respective wind turbine tower apparatus 100 in good andpoor weather, and be able to pass slowly in close proximity to each windturbine tower apparatus 100 for deploying and recovering maintenancecapsules 10 even in the worst weather. When the weather is good, andwhen there is no need to service other wind turbines 101, maintenancevessel 300 can be positioned and maintained on station in closeproximity to the specific wind turbine tower apparatus 100 for a minuteor two while deploying an appropriately preselected maintenance capsule10. Maintenance vessel 300 may then stand off while required maintenanceis performed. Afterwards, maintenance vessel 300 can recover maintenancecapsule 10 while vessel 300 is in close proximity to wind turbine towerapparatus 100. If the weather worsens to levels where it becomesdifficult to recover a maintenance capsule 10 directly on board,maintenance vessel 300 may have to be positioned to recover themaintenance capsule 10 from the sea, at a safe distance from the windturbine tower apparatus 100. The use of azimuth thrusters located belowvessel 300 to propel and hold the position of vessel 300 against watercurrents and wind may be considered necessary in some instances. Theseazimuth thrusters may be electrically powered Azipods as developed byKvaerner Masa-Yards and registered by ABB. Kvaerner Masa is a builder inHelsinki, Finland which built the unique electric Azimuthing AzipodPropulsion System. The latter system, unlike convention propulsion,pulls a ship through the water rather than pushing it. This developmenthas led to an increase in propulsion efficiency and resulting in fuelsavings. The use of Azipods eliminates the need for rudders, long heavydrive shafts, conventional drive units and stern thrusters. It occupiesless space on board the vessel.

Maintenance vessel 300 should be able to hold a series of maintenancecapsules 10 for use at various wind turbines in a wind farm. Referringto FIG. 7, up to forty capsules 10 may be carried. Although for verylarge wind farms, larger vessels with more and varied capsules may beadvantageous.

Maintenance vessel 300 should be expected in some conditions to operateunder poor visibility conditions, such as during dense fog. Maintenancevessel 300 should be provided with thermal imaging equipment to enablethe captain of vessel 300 to see through the fog or other visionobscuring material to safely perform the required duties.

Vessel 300 includes L/R cradles 302 (FIGS. 2, 9, 9A, 9G and 12 asdiscussed below) located on a deck 315 (FIG. 9G) on the top of anelevator bed 322 (FIGS. 8, 10 and 11) at the stern of vessel 300. L/Rcradle 302 is used to deploy and recover maintenance capsules 10 in goodto moderately bad weather. A lower bay 306 is located on the other sideof vessel 300 from upper bay 304 (FIG. 7) around the waterline of vessel300 into which capsules 10 are winched from the sea and brought on boardvessel 300 in very bad weather.

It may become necessary in poor to severe weather conditions to havemaintenance vessel 300 distance itself from wind turbine tower apparatus100 to safely snag towrope 80 for pulling maintenance capsule 10 intolower bay 306 (FIG. 7) of maintenance vessel 300. In order to cope withthis condition, the end of cable or towrope 80 may be propelled therequired distance by the use of pyrotechnics, small rockets, compressedgas guns, small electrically or otherwise powered miniature homing boatsor other means (as described below). If cable 80 is too stiff or heavyto be dragged or propelled the requisite distance from the capsule onboard the wind turbine tower apparatus 100, it may become necessary toutilize a length of light, strong precursor rope (as discussedpreviously and below) attached to the end to permit the overly stiff orheavy cable or towrope 80 to be dragged on board maintenance 300, afterthe precursor has been snagged and wound up.

Maintenance vessel 300 is shown in further detail in FIG. 8. The partsshown in FIG. 8 are used respectively in calm to moderate weatherconditions, and rough weather conditions. With respect to calm tomoderate sea condition, L/R cradle 302 is employed to deploy and recoverthe capsule. With reference to FIGS. 9, 9A-9I, 10 and 11, each L/Rcradle 302 is composed of a pair of oppositely disposed connected cradleparts 312 and 314, underneath of which is an electric drive system 316(FIG. 9A) which propels maintenance capsules 10 around a looped path 317(FIG. 7) internally below upper surface or deck 303 of maintenancevessel 300 to allow the selection of an appropriately preconfiguredcapsule 10 Other types of path such as one with capsules racked oneither side feeding a central path are possible, as shown in FIG. 7A.FIG. 7A shows a set of maintenance capsules 10 located in parallellinear locations 325 and 326, which are moved linearly in L/R cradles302 along a linear path 321 from lower bay 306 to either of parallel,linear locations 325 and 326. Cradles 302 could also come from and bedelivered to upper bay 304. Each of cradle parts 312, 314 includeopposing upstanding walls 308, 310, and L/R cradle 302 has retainingmembers in the form of rollers 319 held by brackets 331 for engaging acooperating portion of maintenance capsule 10 such as a groove 398(FIGS. 1 and 12) in truncated conical outer wall 72 (as discussed below)to hold capsule 10 releasably fixed in L/R cradle 302. Rollers 319rotate in the direction shown by arrows 330. Cradle parts 312 and 314are partially separated by an opening 332 (which could be a hole) forreceiving cable or towrope 80 of maintenance capsule 10. L/R cradle 302also has orienting assemblies in the form of four orienting arms 318 formaintaining capsule 10 in a vertical orientation, with orienting arms318 being disposed in each of opposing upstanding walls 308 and 310which are inclined from outwardly spaced upper or free ends (as shown inFIG. 9) towards each other at their lower narrowly spaced connectedends. The movement of orienting arms 318 is shown by the arrows 329. Anelevator structure 320 (FIGS. 8, 10, 11) is located in bay 304 and isselectively moved up and down to raise and lower L/R cradle 302 betweena position recessed in upper bay 304 and located near upper surface ordeck 303 of vessel 300.

Elevator structure 320 shown in FIG. 11 has an elevator supportstructure 323 which includes elevator bed 322 and opposing pairs ofcolumns 324 extending at right angles to bed 322, and a track system orguiding structure 402. The latter is in the form of three tracks orinverted T-shaped slots 410, 412 and 414 in bed 322. The middle slot isdrive-and-guide slot 422. Slots 410 and 414 are located in bed 322.Slots 410 and 414 are guide slots. Slots 410, 412 and 414 further runalong deck 315 below deck 303 and extend around looped path 317 shown inFIG. 7 or linear path 321 in FIG. 7A. Further included in bay 304 forcooperating with columns 324 of elevator structure 320 is alifting/lowering structure 305 (FIG. 10). Lifting/lowering structure 305includes opposing pairs of grooves 328 (only one pair is visible in FIG.10) in opposing side walls 327 of bay 304 for receiving and guidingcolumns 324. Slot 412 is provided for receiving and engaging electricdrive system 316 of L/R cradle 302.

Maintenance vessel 300 has a travel structure 470 (FIG. 9C) for beingoperatively engaged by the respective L/R cradles 302. In the preferredembodiment, travel structure 470 is composed of a guiding structurewhich could be a variety of forms, preferably a track system 472 (FIGS.9B, 9C, 9E, 9F) discussed herein and a pair of gear racks 422 attachedto slot 412 as discussed below. Electric drive system 316 cooperateswith travel structure 470 to effect movement of L/R cradles 302 as alsodescribed below.

Electric drive system 316 is composed of a drive device 416 (FIGS. 9B,9C and 9F), which is in turn composed of electrical wheel drivingapparatus including a pair of rear drive shafts 418 and their respectivepower apparatus for turning shafts 418 (not shown, but would be anappropriate type of preferably electric motor and gear box for rotatingthe shafts, to be determined by one skilled in the art), a rotatablemechanism 415 in the form of a pair of gears 420 (alternativearrangements are shown in FIGS. 9B and 9F, and described below), wheelstructures including friction-reducing wheels 424 mounted on axles 426for reducing the friction of said L/R cradles 302 as said cradles 302move on vessel 300, and guide rollers 428 mounted on vertical guidewheel support axles 430. Gears 420 rotate in opposite directions asshown by arrows 419 and 421. Travel structure 470 includes gear racks422 which are mounted parallel to side walls 425 (FIG. 9E) of drive slot412 and which are engageable by gears 420. Referring first to FIG. 9B,parallel gear racks 422 are shown which define path of motion of L/Rcradle 302. A support 432 is shown through which parallel gear drive orgear shafts 418 extend, the axes of rotation of drive shafts 418 lyingin an imaginary plane perpendicular parallel gear racks 422. Referringto FIGS. 9B-9F, pairs of gear shafts 418 rotate in the oppositedirections at the same speed except at corners to drive their respectivegears 420 in a synchronized manner. Gears 420 engage racks 422 to driveL/R cradle 302 in either direction in slot 412. Referring to FIG. 9Cwhich shows a drive device 416 in plan view, gear 420 shown in the upperpart of the drawing rotates in the clockwise direction while gear 420shown in the lower part of the drawing rotates in the counterclockwisedirection as shown by respective arrows 419 and 421 to drive L/R cradle302 to the left as shown by an arrow 423. As shown in FIG. 9B, and asnoted above, gears 420 are mounted on axles 418 whose axes of rotationare perpendicular to the imaginary plane of motion of gear racks 422.The same result can be achieved with the arrangement shown in FIG. 9F,where gears 420 are longitudinally offset from each other between gearracks 422, although both driving assemblies for L/R cradle operatevirtually identically. One advantage of the arrangement shown in FIG. 9Fis that the distance between gear racks 422 can be lessened since theaxes of gear shafts 418 are closer together between gear racks 422 andthe top slot can be narrower.

In order to keep L/R cradles 302 properly centered in slot 412, guiderollers 428 are at opposite ends of support 432 and rotate on verticalguide wheel support axles 430 which are vertical to deck 303 ofmaintenance vessel 300. The diameter of guide rollers 428 is sufficientto engage one or the other of sides 434 of slots 412 as shown mostclearly in FIG. 9E, said diameter being marginally smaller than thewalls of slot 412.

In order to keep L/R cradle 302 properly aligned and not subject tounduly bob left and right, L/R cradle 302 comprises an alignment andstability apparatus 435 (FIG. 9A). Apparatus 435 includes a pair ofidler assemblies 436 (FIG. 9H) are provided which are mounted in, andpartially extend through openings 438 in the bottom of L/R cradle 302 asshown in FIG. 9A. Idler assemblies 436 ride in each of slots 410 and 414as shown in FIG. 9G while supporting, restraining vertically and guidingL/R cradle 302 laterally.

Each idler assembly 436 (FIG. 9H) is composed of a vertical idler shaft440 which can rotate as indicated by an arrow 442. Idler shaft 440 has arecess 444 so that it can be accommodated between the narrow parts ofinverted T-shaped slots 410 and 414. Recesses 444 are deep enough sothat the upper walls defining the length of slots 410 and 414 can passunimpeded through recess 444. An axle support 446 is fixed to idlershaft 440, and has a pair of yokes 448 for supporting a pair of verticalaxles 450 which hold a pair of guide or idler rollers 452. Shaft 440also has extending through it a wheel-holding, horizontal axle 454 whoselongitudinal axis is perpendicular and intersects the longitudinal axisof idler shaft 440, as well as being perpendicular to the planeintersecting the longitudinal axes of axles 450. A pair of wheels 456 ismounted for rotation on axle 454. Idler shaft 440 is shown as mounted inL/R cradle 302 and slot 412 in FIG. 9I and supports a thrust androtational bearing 460 for reducing the friction that otherwise wouldoccur as idler shaft 440 rotates in the base of L/R cradle 302 throughwhich opening 438 extends. A groove 461 can be provided in each idlershaft 440 with a corresponding annular groove 462 in each of cradleparts 312 and 314 (cradle part 314 with idler assembly 436 is shown inFIG. 9I, and an identical assembly is in cradle part 312). Ball bearings463 are located in grooves 461 and 462. Alternatively, crossed rollerscould be used. Slots 410 and 414 have opposing side walls 464 and 466respectively as shown in FIG. 9G, and idler rollers 452 (FIGS. 9H and9I) engage the respective side walls 466 and 464 to properly locatewheels 456 in slots 410 and 414 and the mechanism for driving L/R cradle302 in slots 412.

Referring to FIG. 12, each of cradle parts 312 and 314 has a capsulesafety holding mechanism 386 for preventing the inadvertent removal ofcapsule 10 from cradle 302. Capsule safety holding mechanism 386includes rollers 319. Rollers 319 are mounted for rotation on axles 388of pivotally mounted arms 390 in each of cradle parts 312 and 314. Arms390 are mounted respectively on a respective pivot 392 and loaded byforce applying structure such as respective springs 394 and biasedtowards respective openings 396. Rollers 319 engage groove 398 oncapsule 10 to prevent capsule 10 from being pulled out of cradle 302until a large enough upward force 400, as shown in FIG. 12, is exertedby a capsule release structure such as by winch 224 (FIG. 4) which maybe in trolley 124. This prevents capsule 10 from being pulled out ofcradle 302 during rough seas and accidentally falling overboard. L/Rcradle 302 is driven into position in bay 304, by electric drive system316 driving in slot 412 and idler assemblies 436 in slots 410, 414 andcolumns 324 of elevator structure 320 which is elevated if necessary,columns 324 being guided by sliding in grooves 328.

Referring to FIGS. 8, 13 and 14, a capsule transit airlock compartment336 is provided adjacent to and forward of upper bay 304 for permittinga maintenance capsule 10 to transition from a dry interior portion 337of vessel 300 to the exterior. An airlock door 334 is shown in FIGS. 8,13 and 14 covering an opening between upper bay 304 and transit airlockcompartment 336, airlock door 334 fitting in an airlock door frame 335in a sealing arrangement. Capsule transit airlock compartment 336 has afore bulkhead 339 and a side bulkhead 340, and an airlock door track 341(FIG. 13) which could be either on lower deck 315, on the overhead or onboth the deck and the overhead of capsule transit airlock compartment336. A track engaging structure 344 such as pins or the like areprovided on airlock door 334 for riding in airlock door track 341.Airlock door track 341 maintains both vertical sides of airlock door 334proximal fore bulkhead 339 and side bulkhead 340, as shown by arrows342, so as to leave enough room for L/R cradle 302 with capsule 310thereon with enough room to fit in capsule transit airlock compartment336. An interior airlock door 343 between the dry interior portion 337of vessel 300 and capsule transit airlock compartment 336 is provided.

Likewise, a similar interior airlock door track 355 extends along an aftbulkhead 345 and a side bulkhead 346 of dry interior portion 337.Interior airlock door track 355 could be on lower deck 315, in theoverhead or in both deck 315 and the overhead, of dry interior portion337. Door 343 has a track engaging structure 347 such as pins or thelike for riding in interior airlock door track 355. Interior airlockdoor 343 can close against an interior airlock door frame 384 in asealing engagement. Doors 334 and 343 alternatively swing out of theway, as shown by arrow 348 (FIG. 14) (door 343 would have asubstantially identical swinging apparatus), on a hinge 357 to allowcapsule 10 to enter or leave dry interior 337 of vessel 300. Appropriatesealing in the form of resilient gaskets are provided between the edgesof airlock door 334 and a jamb 350 for door 334. Similar gaskets areprovided for interior airlock door 343 and its interior airlock doorjamb 351, and for severe weather for an outer airlock door 352 and asevere weather inner airlock door 380 as shown in FIG. 7 (the latter arediscussed below). It can be seen that a water line 353 (FIG. 8) islocated below door 343, although the water line could change from timeto time. A viewing station 354 is provided to enable the captain orother personnel on vessel 300 to watch and control the operation of L/Rcradle 302. Alternatively, doors 334 and 343 may be simply hinged so asto rotate about a vertical axis, but this will require additional spacein airlock compartment 336.

With reference to FIG. 10, and further considering bay 304, it can beseen further that a winch 356 is provided for winding up and releasingtowrope 80 extending from a maintenance capsule 10. Towrope 80 extendsthrough a port 358 in the lower part of bay 304. Inverted T-shaped slots410, 412 and 414 are located in deck 303 of bay 304 and in bed 322 ofelevator structure 320, and port 358 is located in slot 412. Door 334 isprovided at the forward part of bay 304 (see also FIGS. 13 and 14) forenabling the transfer of maintenance capsules 10 into or from dryinterior 337 of vessel 300 where other capsules 10 are stored for use.

FIG. 11 shows elevator structure 320 in further detail, and furthershows shock absorbing members preferably as shock absorbers or hydraulicrams 360. Elevator structure 320 is composed of four upstanding columns324, rectangular in cross section which each ride in grooves 328 (alsorectangular in cross section) (FIG. 10) disposed in the opposing sidesof bay 304. Each shock absorber 360 is a hydraulic shock absorber havingoil inlet and outlets 362 to a hydraulic system (not shown) withpressure relief valves provided in a respective cylinder 364 for each ofshock absorbers 360. Cylinders 364 are hydraulic cylinders which bothelevate bed 322 and act as shock absorbers by virtue of having pressurerelief on the down stroke only. These reduce the deceleration felt byoccupants of capsules 10 during rough weather recoveries, and allow theraising and lowering of elevator structure 320.

Considering FIGS. 8, 10 and 15, a severe weather recovery ramp assembly366 includes a raisable ramp 368 which is movable between an openposition shown in solid lines in FIGS. 8, 10 and 15 and a raisedposition (shown by arrows 370) indicated in dotted lines in FIG. 15. Arough weather viewing station 372 (FIGS. 8 and 15) is located aboverecovery ramp assembly 366 to enable the captain or other personnel ofmaintenance vessel 300 to observe the movement of a maintenance capsule10 during a severe weather recovery via raisable ramp 368. As shown inFIG. 15, a winch 374 is used to pull cable or towrope 80 extending frommaintenance capsule 10 thereby pulling said capsule 10 into a severeweather airlock 376 as shown in FIGS. 7 and 13. Access to and egressfrom severe weather airlock 376 is by way of outer airlock door 352(FIG. 13) and an inner airlock door 380 (FIG. 7). When raisable ramp 368is in the raised position, it in effect substantially seals maintenancecapsule 10 from the effects of the sea and the weather. In preparationfor a severe weather capsule recovery, ramp 368 is lowered and onlyouter airlock door 352 is opened. Outer airlock door 352 is shown bydotted lines in its open position. When door 352 is in its fully-openposition, its inwardly facing surface (on its right side as shown inFIG. 13) is coplanar with the walls of severe weather airlock 376 toallow capsule 10 to pass through. Outer airlock door 352 pivots in thedirection shown by an arrow 378 (FIG. 13) to its fully-open position. Assoon as capsule 10 is on board, ramp 368 is raised, and when capsule 10is within the bounds of severe weather airlock 376, outer airlock door352 closes and the capsule 10 is cycled into interior 337 of vessel 300for refurbishing and reuse.

For the items described above whose operation is described below, vessel300 has certain requirements for a wind farm of up to 200 wind turbinetower apparatus. Vessel 300 should be able to hold about fortymaintenance capsules 10, associated equipment, turbine spare parts andpersonnel. As stated earlier, the length L.sub.v of vessel 300 ispreferably about 100 meters long, the width W.sub.v is preferably about12 meters wide and its height H.sub.v is preferably about 12 metershigh. The weight of vessel 300 would be about 800 tons, with a capacityof about 200 tons of maintenance capsules 10. Vessel 300 preferably hasa cruising speed of about 35 km/hour, a maximum thrust of about 0.15 gor 150 tons, a range of 1000 km and with a monohull as the hull type.The type of engines would determine the fuel economy. Some degree ofstabilization would be required for the range of motions and degrees offreedom (roll, pitch, heave, yaw, sway and surge).

Turbine tower 102 has at its upper portion a nacelle 550 shown in FIGS.21 and 22 and discussed below. Nacelle 550 houses the equipment foroperating the control and rotation of turbine vanes 103. The systemdescribed below includes some of the components previously describedwith some variations and modifications.

Once the maintenance personnel and parts, equipment and tools aretransferred to the service platform 126 of the wind turbine, there is afurther utilitarian requirement, that is, to move the said maintenancepersonnel and parts, equipment and tools to the most likely placerequiring these, i.e., nacelle 550 of the wind turbine.

Maintenance personnel may be safely moved from platform 126 to nacelle550 by an internal personnel elevator, but heavy, bulky parts, equipmentand tools may prove too heavy and difficult to maneuver through anaccess door to service platform 126, and thence up and into nacelle 550.The interior of nacelle 550 contains a large gearbox, electricalgenerator and associated electrical equipment, much of it on thecentreline of nacelle 550 and over the center of tower 102, makingaccess for large items from the interior of tower 102 onto the generatorfloor of nacelle 550 somewhat problematic. Thus, an exterior cargoelevating system is deemed to be necessary.

It should be noted that an external cargo elevator capable oftransporting materials from service platform 126 via a towersurface-mounted guide track could have the said track extendingdownwards to sea level. This would allow, foundation type allowing, incalm weather, the direct transfer of material from maintenance vessel300 to the cargo elevator and, thence, to nacelle 550. This avoidshaving the lifted load swinging dangerously in the wind from a longcable, extending downwards from a mounted crane on nacelle 550 to amaintenance vessel, as is currently done.

In strong winds, even when waves are within the capability of proposedor existing transfer systems which could place personnel and materialson the service platform, the lowering of a cable over a hundred metersto pick up a load and raise it to the nacelle can result in the loadswinging uncontrollably and smashing disastrously into the side of thetower during the lift. Thus, heavy, bulky items necessary formaintenance could be stranded on the service platform until theoffending winds subside.

The discussion to follow represents some modifications to the detaileddescription previously set forth with respect to FIGS. 1-15. The samenumerical identifiers will be retained for previously describedcomponents.

Referring to FIG. 16, a fixed maintenance or non-swivelling crane 500 isshown. Fixed maintenance crane 500 faces downstream and has a crane boom502 extending horizontally outwards from an attachment point 504 locatedabove platform 126. Said crane 500 is located at an elevation aboveplatform 126 such that when cargo compartment access door 28 opens ontothe platform 126, the floor of the cargo compartment is approximatelylevel with the top of platform 126 to allow a box or frame 600(discussed below) to be rolled outwards or inwards from platform 126.

Crane boom 502 is both supported and prevented from rotating upwardsabout attachment point 504 by rigid braces 508, 510, 512, 514. A trolley800, different from trolley 124 and described below, may be driven alongcrane boom 502. Rigid braces 508, 510, 512 and 514 could have variousconstructions for holding their respective loads and could have theconstruction of the components of crane assembly 104 discussed earlier.

It should be noted that, if the general downstream direction is known,the maintenance crane 500 can be permanently mounted in that direction,obviating the necessity for a swinging mechanism. This can result in amuch simpler, smaller, lighter and less expensive structure. The meansby which the movement of parts, equipment and tools is achieved requiresthat they be moved upwardly along the side of tower 102, then around toa location below a crane mounted on nacelle 550, and thence finallyupwardly towards a nacelle access platform (discussed below) outside ofnacelle 550, from which they may be put to use inside nacelle 550. Thispermits use of these items in even the most severe winds, makingmaintenance possible throughout the entire year, as a cargo crane 560does not have to lower its cable hundreds of feet to access platform 126or even lower to vessel 300 to have said cable oscillating wildly in thewind.

Power, hydraulic power hoses, control cables and any other necessaryservices transmitted along services transmitter lines 523 (FIG. 17) maybe conducted within turbine tower 102 and along crane boom 502 to alocation near its midpoint. There is another embodiment of the inventionwhich is considered to be an improved system for moving a trolley alonga crane boom. This is described below. Direct continuous connection ofservices to trolley 800 as it moves along crane boom 502 may be achievedby use of a modular carrier or flexible services carrier 518 connectedtogether as shown in FIGS. 17-19. Modular carrier 518 is made ofcorrosion-resistant materials and plastics such as those manufactured byGortrac Division of A&A Mfg. Co. Inc. or others. Modular carriers 518are described in detail below.

Modular carriers 518 as provided by the foregoing Gortrac Division canbe Gortrac's Nylatrac®. Open-Style Modular Carriers which areconstructed from standard components which can be modified to achieve ahigh strength, customized engineered carrier system. Modular carrier 518can essentially have the features shown in FIGS. 20 and 20A, butvariations and modifications would have to be made depending on thecharacteristics of each system in which the modular carrier 518 is used.Modular carrier 518 would comprise a series of chain links or carriers1001, as shown in FIG. 20. Each chain link 1001 is composed of a sideplate 1003 having an axle hole 1005 at either end. Each axle hole 1005has an axle 1007 extending therethrough, and each side plate 1003 isattached to a separate offset plate 1003′. Each side plate 1003 isattached to an opposing side plate 1003 and connected thereto by crossbars 1009, and each offset side plate 1003′ is attached to an opposingoffset side plate 1003′ and connected thereto by a cross bar 1009′.Modular carrier 518 is similar in construction and flexibility to abicycle chain. The details of the Gortrac modular carrier could beobtained through their email address sales@gortrac.com.

Due to possible electromagnetic interference between electric powercables and control or communication cables, two carriers 518 may, benecessary, located on opposite sides of crane boom 502. Each modularcarrier 518 would rest on a low services carrier tray 520 and a highservices carrier tray 524 as shown in FIGS. 17, 17A, 18 and 19 attachedone carrier height above, on each side of crane boom 502 as required. Anupper end 534 of modular carrier 518 is fixed and proximate to a rigidservices tube 522 which is connected to the top of trolley 800. A lowerend 536 of modular carrier 518 is located on the side of crane boom 502.Rigid services tube 522 is connected between trolley 800 and upper end834 of modular carrier 518. Rigid services tube 522 holds servicestransmitter lines 523 running from modular carrier 518 to operationaldevices in trolley 800 such as transportation devices, computer systems,hydraulically operated devices, etc., to which services transmitterlines 523 are connected to transmit whatever medium is transmitted bythe respective services transmitter lines 523 to the foregoing devices.Modular carrier 518 is connected to trolley 800 and is somewhat longerthan the length of the travel of trolley 800 and is directedhorizontally away from attachment point 519 proximate the end of tray520 closest to the midpoint of boom 502 (it is assumed that servicestransmitter lines 523 extend from turbine tower 102).

Referring to FIGS. 17 and 17A, trolley 800 includes a body portion 802having roof 804 with an orifice 806 through which a gear drive 808extends. Stepped channels 810, 812 extend longitudinally on the upper,outer sides of trolley 800. Axles 818, held by axle holders 814, extendthrough outer walls 816 of channels 810, 812 for guiding andweight-bearing wheels 820. Another set of lower axles 822 support a setof lower wheels 824 in the lower part of channels 810, 812, and guidingand upward force-resisting upper inboard axles 821 support guiding andweight-bearing wheels 819.

A loop 532 of modular carriers 518 moves between upper end 534 at anentrance and 530 of rigid services tube 522 and a lower end 536 on roof804 of trolley 800. Upper end 534 of modular carrier 518 is higher abovethe path of trolley 800 than is lower end 536, and modular carrier 518droops and forms a looped-over portion 532 as carrier 518 proceeds fromupper end 534 slides to lower end 536.

As shown in FIGS. 17 and 17A, drive gear 808 engages a rack 517 fixed tothe underside of crane boom 502. Lower wheels 824 are used to preventexcess upward movement of trolley 800 due to connection to any upwardlymoving load such as maintenance capsule 10 during transfer operationsfor maintenance personnel and their tools, equipment and parts. Aweather/rain cover 842 extends from crane boom 502 and covers rigidservices tube 522, wheels 820 and services carrier tray 520. Anotherweather/rain cover 844 extends from crane boom 502 and covers wheels 820on the opposite side of trolley 800 from rigid services tube 522 if asecond services carrier is not necessary.

Services transmitter lines 523 carry the services for operating trolley800 and could include electrical transmission services in the form ofelectrical conductor cables, control signal services, hydraulic systemservices and the like. In some cases, such as power cables and signalcables, a physical separation of such cables may be necessary.Therefore, a second modular carrier similar or identical to modularcarrier 518 would be located on the opposite side of trolley 800.

If trolley 800 starts in close proximity to turbine tower 102 andtravels outwardly along crane boom 502, the looped-over portion 532 ofcarrier 518 would then droop downwardly until it comes into contact withthe upper surface of its lower portion and slides upon itself. Astrolley 800 passes near the midpoint of crane boom 502, upper end 534 ofmodular services carrier 518 passes over lower attachment point 519 andthence onto a high support tray 524 upon which it slides as trolley 800continues to move outwardly from turbine tower 102. The set of lowerwheels 824 on top of trolley 800 is used to prevent excessive upwardmovement of trolley 800 due to connection to any upwardly moving load,such as a maintenance capsule 10 during transfer operations formaintenance personnel, their tools, equipment and parts. The set oflower wheels 824 are shown in FIGS. 17 and 17A.

Referring to FIGS. 21, 23 and 24, a cargo elevator 700 for carryingweatherproof storage box or frame 600 having casters 602 to permitstorage box 600 to be easily rolled, with minimal effort, on a floor ordeck 127 of access platform 126 (FIG. 16), on or off cargo elevator 700,and on a nacelle access platform 552 and thereafter into nacelle 550.Nacelle 550 also includes a generator 1002.

Storage box or frame 600 preferably has opposing bottom edge orshoulders or side recesses 604 (FIGS. 22, 23, 23A and 24), which canalso be an extra-tall storage box 600′ as shown in FIG. 23. Siderecesses 604 have horizontal surfaces defining which are capable ofsupporting storage boxes or frame 600 or 600′ by movable latches 870 incargo carrier 850, as described below.

A pair of L-shaped parallel elevator guide tracks 722 extend verticallyon tower 102 from below recessed opening 706 to nacelle 550 and haveparallel track legs 752 and coplanar track arms 754.

Cargo elevator 700 (FIG. 22) has on its upper portion a platform orshelf 701, three sides of which have fixed side walls 708 and oneremovable wall 712. Cargo elevator 700 operates out of an accessplatform recessed opening 706 in floor 127 of access platform 126 toreceive box or frame 600. Elevator guide tracks 722 may extenddownwardly to below the surface of the sea to permit the placement of abox 600 directly on cargo elevator 700 from maintenance vessel 300 incalm weather. Elevator 700 further is composed of a lightweightstructural frame 702. Structural frame 702 has a cargo elevator truck704 holding retention wheels 707 on axles generally tangent to turbinetower 102, and side guide wheels 711 on axles generally perpendicular tothe axles of retention wheels 707. The function of wheels 707 and 711are discussed below. Elevator 700 may be positioned such that the uppersurface of cargo elevator platform 701 is at the same height as theupper surface of platform 126 when cargo elevator 700 is positioned forloading or unloading at access platform 126. A guard rail 732 and gates734 surround recessed opening 706 to prevent personnel from falling intoopening 706 when elevator 700 is not present.

Cargo elevator 700 moves along guide tracks 722 by means oftrack-engagement-and-traveling assembly 710. The latter assemblycomprises holding retention wheels 707 and side guide wheels 711. Cargoelevator truck 704 is guided and restrained laterally by cargo elevatorguide tracks 722. Retention wheels 707 of truck 704 resist the momentapplied by the load on cargo elevator 700 in the direction away from thevertical axis of the wind turbine tower 102 and side guide wheels 711maintain truck 704 in guide tracks 722.

Movable cargo elevator 700 is attached to a cargo elevator cable 724 viaa lifting lug 709 on elevator truck 704. A cable attachment structure728 includes cargo elevator cable 724 and a cable lifting-and-loweringapparatus 733, which includes a pulley 726, a horizontal axle 727 onwhich pulley 726 is rotatably mounted and a winch 730. Pulley 726 ismounted for protruding out of tower 102 below nacelle 550 of turbine 100to be connected to winch 730 which is used to raise or lower elevator700 as desired. The movement of movable cargo elevator cable 724 isshown by an arrow 729 in FIG. 21. A rain cover 731 (FIG. 22) is utilizedto prevent severe weather from driving salty sea spray or rain into theinterior of the tower 102 where such materials could promote interiorcorrosion.

Due to wind, cargo box 600 on cargo elevator platform 701 will tend tobe blown sideways, so fixed set of sturdy guard railings 708 withstanchions 714, 715, and removable guard railing 712 in the entryway toplatform 701, are used to restrain the cargo laterally, as shown in FIG.24. On the side where cargo box 600 is rolled onto platform 701, asturdy hinged or removable blocking device in the form of tool and/orparts storage box blocking bar 716 is provided which can be fixed orlatched to opposing side stanchions 715 and is used to prevent box 600from rolling off the cargo elevator platform 701 in severe windconditions during transit of elevator 700 up or down the turbine tower102.

When cargo elevator 700 carries the box 600 up the side of tower 102,nacelle 550 may not be in a position where elevator 700 may transfer box600 onto nacelle access platform 552. Thus, it is desirable to move box600 around the periphery of tower 102 to a position under a cargo hatch556 of nacelle access platform 552. Referring to FIGS. 21 and 23,nacelle 550 has cargo crane 560 that may lower a storage box line in theform of a cable 562 thereof, and maintenance personnel can then urge alifting hook 564 to engage a lifting lug 606 of box 600. Cargo crane 560can be used to lift box 600 sufficiently to allow cargo hatch 556 to beclosed, allowing box 600 to be lowered onto the upper surface of hatch556 which is then flush with platform 552 of nacelle 550 so that it maybe rolled around on its castor wheels 602 on said surface as may bedesired, and to enter nacelle 550 where the contents of box 600 may beutilized by maintenance personnel to effect the appropriate maintenance,etc.

The means by which box 600 may be moved around the periphery of tower102 can be a cargo carrier 850, as shown in FIG. 21, which travels on aset of circumferential guide tracks 852, which support and guide cargocarrier 850 as it drives around the periphery of turbine tower 102, justbelow nacelle 550. With reference to FIG. 23, cargo carrier 850comprises a holding frame 851 holding a tool and/or parts storage box600. Cargo carrier 850 is restrained horizontally by a minimum of threevertical axis wheels 854 turning on vertical axles 856 affixed tooutstanding portions 858 of cargo carrier 850. Cargo carrier 850 extendsas a cantilever from parallel guide tracks 852. There are twocircumferential guide tracks 852 shown, although other numbers of guidetracks 852 could be used depending on operating conditions. Eachcircumferential guide track 852 comprises a sideways, inverted L-shapedflange having a radial, horizontal flange part 853 extending radiallyfrom the turbine tower, and a vertical flange part 855 extending fromexterior end of horizontal flange part 853. Cargo carrier 850 issupported vertically by a minimum of two horizontal axis wheels 860running on horizontal flange part 853 of guide tracks 852. Wheels 860turn on horizontal axles supported by an outstanding portion 864 ofcargo carrier 850.

Holding frames 851 is composed of a light, strong, rigid structuralframe 866 with a vertical aperture 867 capable of passing box 600therethrough from the upper portion of cargo elevator 700. A set ofhorizontal receptacles 872 has the set of horizontally movable latches870 (FIG. 23) which are part of cargo carrier 850 and which moveinwardly therefrom to engage and support box 600 via recesses 604.Latches 870 may be moved inwardly or outwardly from apertures 872 incargo carrier 850 to engage or disengage box 600 remotely byelectro-mechanical or other actuator devices under the control ofmaintenance personnel or otherwise, when cargo elevator 700 is situatedat the top of a cargo elevator guide track 720, and latches 870 supportthe entire weight of box 600 when the downward-facing portion of recess604 is just above the otherwise supportive latches 870, so that saidlatches 870 when fully extended into vertical aperture 867, box 600 maybe moved without being frictionally engaged by the latches 870 as it ishoisted out of the cargo carrier. Cargo carrier 850 further has arestraining bar 873 for restraining box 600 against movement on cargocarrier 850.

Turning next to FIGS. 25 and 25A-25C, a driving mechanism such as a rackchain drive 900 may be used to urge cargo carrier 850 around theperiphery of turbine tower 102 with box 600 partially or totally withinaperture 867, supported by latches 870 engaging recesses 604. A cargocarrier ring-locking structure 1020 in the form of a rack chainconnector 874 (FIG. 23) of cargo carrier 850 is provided to allow apositive connection to the rack chain drive 900 via connectors 932. Acargo carrier ring-locking structure 1020 locks cargo carrier 850 toconnector 932. This is shown in FIG. 23.

Gates 734 of access platform 126 are swingable through an arc indicatedby arrows 735 as shown in FIG. 24. Gates 734 are moved to their openposition once platform or shelf 701 of cargo elevator 700 is even withdeck 127 of access platform 126 to enable wheeled storage box 600 to bemoved on or off platform or shelf 701 along the path shown by arrows736.

Still referring to FIG. 23, it is likely that turbine tower 102 is notperfectly circular since it is more than six meters in diameter, so thata rigid ring gear with internal teeth would be expected to experiencevariable clearances if it were to be rotated around the periphery of theturbine tower 102 in proximity to cargo carrier 850. Therefore, such aring gear would experience unacceptable friction and wear of therespective contacting surfaces and variability in meshing of the gears.Furthermore, such a large ring gear would also be extremely difficultand costly to manufacture. An alternative might be a roller drive chain.However, if a roller drive chain were driven in a circular path around alarge diameter object, this would require a horizontal supportivesurface to avoid damaging sagging between the drive mechanism and thedriven object. Also, if such a horizontal, supportive surface werepresent to support a commonly available drive chain, there would beconsiderable friction and wear on both the downward side of the chainand the top of the supportive surface where they contact.

Accordingly, with reference to FIGS. 25 and 25A-25C, rack chain drive orring 900 in the form of an endless rack drive chain 901 is shown. Rackdrive chain 901 is made of a rigid, corrosion resistant material such asa reinforced self-lubricating plastic. Rack drive chain 901 is composedof individual chain segments 902 which are also shown in FIGS. 25A, 26,27 and 27A-D. Rack drive chain 901 has connective outstanding portions903 at one end of chain segments 902, and outstanding portions 903 haveconnecting vertical holes 905. A corresponding inversion 907 (FIGS. 25,27B and 27D) at the other end has two vertical access holes 909, both ofwhich receive a connecting pin 906. Connecting pins 906 connect segments902 end-to-end with each other to permit the construction of endlesschain 901. Further, each pin 906 is fitted with a wheel 908 on opposingsides of each segment 902, such that when rack drive chain 901 isclosely wrapped around turbine tower 102, there is a clearance C shownin FIG. 25B between the innermost tips of respective gear teeth and theouter edge of turbine tower 102 as wheels 908 ride on the outer surfaceof turbine tower 102, avoiding friction between the inward-facing gearteeth and the tower 102.

Referring to FIG. 26, it can be seen that each chain segment 902 isidentical with each other except for one or more special segments 904. Aperspective view of a chain segment 902 is shown in FIG. 27. Segments904 are selected from a set of special segments which have a decreasingintegral number of teeth as compared to each “typical” segment 902, sothat excessive clearance between rack drive chain 901 and the outersurface of turbine tower 102 can be adjusted as required for initialinstallation, or to compensate for wear or stretching of rack drivechain 901 in service. This is accomplished by removal of one or moresegments 902 and replacement with appropriate shorter special segments904. Each chain segment 902 has an internal gear rack 913 which formsthe interior respective segments 902.

Since rack drive chain 901 is to travel around turbine tower 102 on ahorizontal surface on the side of tower 102, a support flange 910 isprovided and is shown in FIGS. 25B and 26. Each chain segment 902 and904 has vertical outstanding flanges 912 shown in FIGS. 25B, 26 and27A-27D, for the installation of at least one support wheel 914 as shownin FIG. 25B. Each support wheel 914 is mounted on an axle 916, as shownin FIG. 25B. Each axle 916 is oriented radially towards the center ofturbine tower 102 so that wheels 914 will roll on, and not skid on,support flange 910. Wheels 908 and 914 each reduce the frictionalresistance to the movement of rack drive chain 901 on its path aroundturbine tower 102.

Axles 916 and each connective pin 906 are secured to respective supportwheels 914 by a locking or securing mechanism 928 as shown in FIG. 25A.Rack drive chain 901 is driven around turbine tower 102 by engagementwith drive gear 918 as shown in FIG. 25. A drive gear 918 protrudesthrough the wall of turbine tower 102 via a slot 920. Drive gear 918 isrotated about a vertical axis 922 shown in FIGS. 25B and 26 by a motorand gear box or other drive assembly, referred to generally by numeral926 shown in FIG. 22. Drive assembly 926 is controlled by themaintenance personnel on board wind turbine 100.

A clutch is preferably provided between a gear box shaft and drive gear918 to permit drive gear 918 (FIGS. 25, 25B and 26) to be disconnectedfrom the assembly 926 when necessary and allow the cargo carrier 850 toremain in synchronization with the access hatch of the nacelle accessplatform 552 while maintenance is in progress. Turning to FIG. 23, theclutch is preferably interconnected with an opening 1010 in a nacellefloor 1012, through which a pin 1011 is inserted to engage a receivinghole 1013 in the upper portion of cargo carrier 850 such that as pin1010 is inserted by maintenance personnel to lock cargo carrier 850 andthe nacelle 550 together. The clutch is caused to be disengaged by anelectro-mechanical device, such that the rotation of nacelle 550 tofollow the varying direction of the wind, and will not back drive thedrive assembly and thereby damaging it. The reverse process, where pin1011 is removed to unlock cargo carrier 850 from nacelle 550, causes theclutch to re-engage to allow rack chain drive 901 to be used to movecargo carrier 850 as desired around the periphery of turbine tower 102.In the area adjacent to drive gear 918, rack drive chain 901 will tendto ride out of engagement with drive gear 918 due to the tooth profileand any slack in rack chain drive 901, so a means of retention in thisarea is necessary. Thus, short length vertical circumferential walls 930(FIG. 26A) spaced outward from the wall of turbine tower 102 on whichwheels 908 ride by a distance equal to the diameter of wheels 908, plusan acceptable clearance, such that engagement of the gear teeth withrack drive chain 901 and drive gear 918, are maintained. Thesecircumferential walls are centered about drive gear 918 and extendcircumferentially for a length not less than two chain segments 902 thathave additional outwardly-angled end pieces to guide rack drive chain901 into proper engagement with drive gear 918.

Cargo carrier 850 connects to rack drive chain 901 by means of cargocarrier ring-locking structure 1020. Structure 1020 includes connectors932 as shown in FIG. 26. Connectors 932 replace spacer washers 934 (FIG.25B) which are normally fitted on connecting pins 906 for connecting oneor more rack drive chain segments 902. Connectors 932 extend beyond thehorizontal extent of restraining circumferential walls 930, as shown inFIG. 26A sufficient to allow connection to a rack chain connector 874 incargo carrier 850 as shown in FIG. 22. In order to allow the freepassage of connectors 932 past circumferential walls 930, upper andlower walls 930 are separated by a gap 933 sufficient to prevent anycontact between themselves and connectors 932 or any portion of cargocarrier 800.

The operation of the preferred embodiment of the invention will now bedescribed. Maintenance vessel 300 with maintenance capsules 10 loaded onboard would travel to a wind turbine tower apparatus 100 in an offshorewind turbine farm along an optimal path to attend to the maintenance ofwind turbine 101 and numerous others as determined by a preventativemaintenance schedule modified by unscheduled problems reported fromvarious turbines via telemetry. As explained earlier, when the weatheris good, there is no need to expedite the maintenance service, andmaintenance vessel 300 would travel into close proximity of a windturbine tower apparatus 100 for a minute or two to deploy an appropriatemaintenance capsule 10. Swivelable crane assembly 104 (or a fixedmaintenance crane 500 discussed below) would be remotely activatedbefore the close approach of maintenance vessel 300 by one or morepersonnel either on wind turbine tower 102 or on board vessel 300.Maintenance vessel 300 would be moved downstream of tower apparatus 100(the downstream direction is defined herein as the direction of drift ofan unpowered vessel in the vicinity of the respective wind turbine towerapparatus 100 most directly away from said wind turbine tower apparatus100). Truss 108 of crane assembly 104 is rotated about tower 102 onlower annular support rail 134 and upper annular support rail 154 (FIG.3) extending around tower 102, to be in the downstream direction ofmaintenance vessel 300 (fixed crane boom 502, shown in FIG. 16, wouldnot be rotated). Trolley 124 (or trolley 800) is activated and caused totravel along truss 108 (or crane boom 502) towards the end of truss 108(or crane boom 502), and capsule attachment line 48 is lowered fromwinch 224, and attached directly to maintenance capsule 10 directlybelow, aboard the maintenance vessel 300. The maintenance capsule 10 isthen lifted to a height just above the level of walkway 126 (FIG. 2, oras shown by an arrow 505 in FIG. 16) by said winch 224, so that themaintenance personnel and equipment can easily be unloaded to walkway126. At this height, maintenance capsule 10 is engaged at its shoulder42 by latch arms 238 (FIG. 4) of latch assembly 236 of trolley 124 (ortrolley 800). When winch 224 winds up capsule attachment line 48, itdoes so through tensioning guide rollers 228 which may be driven tomaintain a minimum suitable tension in said towrope or capsuleattachment line 48 when it is wound onto the drum of winch 224. If winch224 on trolley 124 (or trolley 800) lifts maintenance capsule 10directly from L/R cradle 302 of vessel 300, it should do so at a rateexceeding the maximum vertical speed of maintenance vessel 300 as itrides on the sea. The reason for having maintenance vessel 300 locateddownstream from wind turbine tower apparatus 100 is to prevent vessel300 from colliding with wind turbine tower 102 in the event there ispropulsion engine failure. If the latter occurs, maintenance vessel 300would drift away from tower 102 rather than running the risk ofcolliding with it Thus, in all weathers, the captain would drive vessel300 in reverse generally towards wind turbine tower 102, orientingmaintenance vessel 300 so that its stern or rear end is adjacent to windturbine tower apparatus 100 to enable fast unloading of capsule 10, andto enable it to drive away quickly in case problems arise.

Winch 224 and its associated equipment should be operated remotely.Likewise, swivelable crane assembly 104 should be operated remotely andcaused to rotate about the vertical axis of tower 102 so as to extendits main boom or truss 108 in the downstream direction, and to remotelydrive trolley 124 (or trolley 800) as far as necessary outwardly fromwind turbine tower apparatus 100 in the direction of the free end oftruss 108.

When the capsule attachment line 48 of winch 224 of trolley 124 (ortrolley 800) is lowered to maintenance capsule 10 for locking onto thetop of capsule 10, care must be taken to allow for enough slack incapsule attachment line 48 so that even if the difference between winch224 and maintenance vessel 300 is in a wave trough, capsule attachmentline 48 will not become taut, as this may endanger personnel on boardmaintenance capsule 10 or cause capsule 10 to inadvertently detach fromL/R cradle 302 on vessel 300.

As soon as maintenance capsule 10 is lifted clear of vessel 300, vessel300 should be propelled away from beneath capsule 10. The retractionspeed of capsule attachment line 48 may then be varied as desired, andshould be slowed as maintenance capsule 10 approaches latch assembly 236on trolley 124 (or trolley 800) so that the maintenance personnel aboardwould not be subjected to objectionable or dangerous decelerations whenmaintenance capsule 10 docks with trolley 124 (or trolley 800). Ifaccess door assembly 30 of capsule 10 is not facing wind turbine tower102, the rotational drive of trolley 124 (or trolley 800) should beactivated to rotate capsule 10 on rotational bearings 206 so that accessdoors 28 and 30 can be opened in the direction of access platform 126.

After trolley 124 (or trolley 800) is attached to maintenance capsule10, trolley 124 (or trolley 800) is driven back along truss 108 (orcrane boom 502) until capsule 10 comes alongside platform 126 of windturbine tower apparatus 100. The maintenance personnel swing away thenearest portion of safety fence 128 of walkway 126, and disembark fromcapsule 10 with their equipment and perform the necessary maintenance.

After the required maintenance has been conducted, the foregoing processis reversed. The maintenance personnel load their equipment into cargocompartment 20 of capsule 10 and enter personnel compartment 18. If thesea is dead calm, the capsule 10 may be lowered directly onto L/R cradle302. If the sea is relatively calm, the maintenance personnel may opt tolower recovery cable or towrope 80 from the bottom of maintenancecapsule 10 to L/R cradle 302 of maintenance vessel 300, where personnelof vessel 300 would attach towrope 80 to winch 356 beneath L/R cradle302. There must be enough slack left in towrope 80 for the reasonsexplained above.

The braking system of winch 224 is activated and latch arms 235 aredetached from annular recess 42 of capsule 10. Said braking system isset to a tension equal the weight of maintenance capsule 10 plus anamount to appropriately tension recovery cable or towrope 80 to keep itrelatively straight. Winch 356 of L/R cradle 302 on vessel 300 isengaged to pull maintenance capsule 10 against the tension of thebraking system of winch 224 at a speed exceeding the maximum speed ofwhich maintenance vessel 300 may rise as the sea swells, untilmaintenance capsule 10 sets into L/R cradle 302 which is raised toabsorb the shock of docking and whose shock is absorbed by shockabsorbers 360. Capsule attachment line 48 from winch 224 is forciblydisengaged from the top of maintenance capsule 10, maintenance vessel300 is propelled away from wind turbine tower apparatus 100, andattachment line 48 is retracted.

If the weather has become more severe where it exceeds the capability ofthe system to recover maintenance capsule 10 directly from towerapparatus 100 to L/R cradle 302 aboard maintenance vessel 300, themaintenance personnel in capsule 10 may opt to disengage the attachmentlatch arms 238 and have winch 224 of wind turbine tower apparatus 100lower maintenance capsule 10 into the sea where capsule attachment line48 of turbine winch 224 is forcibly disengaged for a downstream searecovery of the capsule by maintenance vessel 300, and the attachmentline 48 is retracted.

Alternatively, the maintenance personnel may opt to disengage theturbine hoist capsule attachment line 48 from the top of maintenancecapsule 10, and open attachment latch arms 238 to effect the dropping ofmaintenance capsule 10 directly into the sea downstream of wind turbinetower apparatus 100 for a sea recovery by maintenance vessel 300 at asafe distance from tower apparatus 100. Sea recovery entails theejection of floating towrope 80 from the bottom of maintenance capsule10 as it floats on the sea, and the snagging of floating towrope 80 bymaintenance vessel 300 which uses towrope 80 to haul capsule 10 upraisable ramp 368 using a sea recovery winch aboard vessel 300. This isthe same manner in which a whaling ship hauls a dead whale on board.

In severe weather, a different mode is required to transfer maintenancepersonnel and their associated equipment onto wind turbine towerapparatus 100. When the weather is most severe, (unless fixedmaintenance crane 500 is being used) swivelable crane assembly 104 isremotely operated to rotate truss 108 about its vertical axis so as toextend truss 108 in the downstream direction, and drive trolley 124 asfar as necessary outwardly from tower 102 in the downstream direction ontruss 108. Maintenance vessel 300 does as when the weather is calm, haveits stern portion closest to wind turbine tower apparatus 100, with themaintenance capsule 10 to be used on board. Winch 224 (FIG. 4),controlled remotely, is caused to lower its hoist capsule attachmentline 48 with its end float into the sea. Enough cable is reeled out sothat it streams out downstream a safe distance to where maintenancevessel 300 is able to snag capsule attachment line 48. The end ofcapsule attachment line 48 is then locked onto the top of maintenancecapsule 10.

Maintenance vessel 10 is backed up as close as possible to towerapparatus 100 while truss winch 224 continues to take up slack incapsule attachment line 48, rapidly taking in and reeling out line asvessel 300 rises and falls due to the motion of the sea. This occursuntil the angle between capsule attachment line 48 and an imaginaryvertical line reaches an acceptable value. Then, winch 224 is remotelycontrolled to forcibly retract capsule attachment line 48 at a speedfaster than maintenance vessel 300 rises on the sea as the sea swells.This causes capsule 10 to be released from retaining rollers 319 of L/Rcradle 302, lifting maintenance capsule 10 clear of maintenance vessel300. As soon as maintenance capsule 10 is lifted clear, the propulsionsystem of maintenance vessel 300 is engaged to propel it away fromcapsule 10 and consequently wind turbine tower apparatus 100. Theretraction speed of capsule attachment line 48 may be varied, and shouldbe slowed as maintenance capsule 10 approaches latching assembly 235 oftrolley 124 (or trolley 800), when maintenance capsule 10 docks withtrolley 124.

Once maintenance capsule 10 is securely latched onto trolley 124 (ortrolley 800), the maintenance personnel with their associated equipmentare transferred to access walkway 126 of tower 102 as described abovewith respect to calm weather deployment procedure.

Most of the equipment discussed above could be modified from existingapparatus. The components of wind turbine tower apparatus 100, includingwind turbine 101, tower 102 and walkway 126 may be acceptable as theyare presently used in the field. The use of insulated, seaworthymaintenance capsule 10 with its shock absorbing seats 14, above a sealedcargo compartment 20 which restrains tools and parts, is extremely safeeven if capsule 10 is struck or ends up in the sea. The use of thedownstream location of vessel 300 offers added protection even if thereis failure of the propulsion system of vessel 300. Trolley 124 (ortrolley 800) can be operated manually, along with the components oftrolley 124 (or trolley 800), adding another degree of safety. Althoughvessel 300 could be modified from existing vessels, it may be necessaryto produce a new vessel because of the novel features involved.

The invention has been described in detail with particular reference tothe preferred embodiments thereof, and variations and modificationswithin the spirit and scope of the invention may occur to those skilledin the art to which the invention pertains.

The invention claimed is:
 1. A container for use in an offshore wind turbine maintenance program, said container being constructed to safely survive being disposed and briefly submerged in the sea and protect maintenance people and cargo located in said container, said container comprising: an outer wall for said container, said outer wall being seaworthy and watertight for rendering said container floatable; a personnel compartment within said outer wall for holding at least one maintenance person; a cargo compartment within said outer wall for holding cargo; a watertight bulkhead separating said personnel compartment from said cargo compartment; at least one access door assembly for opening and closing said outer wall to said personnel compartment for enabling at least one maintenance person to enter and exit said container; a truncated conical shell including a forward truncated end portion and a rearward truncated end portion of said container, said truncated conical shell further including a forward endmost section and a rearward endmost section; and a capsule attachment line holding-and-releasing apparatus disposed in one of said endmost sections for selectively holding and selectively releasing a capsule attachment line from said receptacle for selectively enabling said at least one container to be moved to or from a wind turbine tower, said holding-and-releasing apparatus including: a receptacle for receiving and discharging a capsule attachment line; and a capsule attachment line engaging apparatus for being secured to a capsule engagement line.
 2. A container according to claim 1 wherein said holding-and-releasing apparatus further comprises: a releasable holding mechanism for selectively holding a capsule attachment line to enable said container to be pulled or released by the capsule attachment line.
 3. A container according to claim 1 and further comprising: an attachment line discharge port for receiving and releasing said capsule attachment line.
 4. A container according to claim 1 and further comprising: a towrope storage compartment for storing a towrope for being grasped to enable the pulling of said container; a homing boat for optionally taking a part of said towing rope to a maintenance water vessel; and a launch tube for storing said homing boat.
 5. A container according to claim 1 wherein said personnel compartment comprises: a seat for supporting a person in said personnel compartment, and a shock absorbing system operatively connected to said seat for absorbing shocks applied to said seat.
 6. A container according to claim 1 wherein a capsule attachment line is received in and paid out in one of said endmost section of said truncated conical shell.
 7. A container according to claim 1 and further comprising an operational compartment and operational compartment outer walls around said operational compartment, and air vents through said operational compartment outer walls to enable said capsule to ventilate air or drain water from said operational compartment when said container is dropped into the sea.
 8. A container according to claim 1 wherein when said container includes a central longitudinal axis extending through said endmost section of said truncated conical shell; when said container is disposed and briefly submerged in the sea, said longitudinal axis approximates the horizontal direction; and wherein said cargo compartment is disposed below said personnel compartment due to the higher weight in said cargo compartment.
 9. A container according to claim 1 wherein said personnel compartment is located closer to said forward endmost section of said truncated conical shell than the location of said cargo compartment.
 10. A container according to claim 1 wherein said capsule attachment line holding-and-releasing apparatus comprises: a barb attached to a capsule engagement line; a holding mechanism for releasably holding said barb and the capsule engagement line having said barb attached thereto; and apparatus for selectively releasing said barb from said holding mechanism.
 11. A seaworthy, watertight, floatable container for use in an offshore wind turbine maintenance program, said container being able to safely survive being disposed in the sea and protect maintenance people and cargo located in said container, said container including: at least one access door assembly for enabling cargo and any maintenance persons to be loaded and unloaded from said container, a capsule attachment line holding-and-releasing apparatus for selectively holding and selectively releasing a capsule attachment line for selectively enabling said at least one container to be moved to or from a wind turbine tower, and a towrope storage compartment for storing a towrope for being grasped to enable the pulling of said container; a homing boat for optionally taking a part of said towing rope to a maintenance water vessel; and a launch tube for storing said homing boat.
 12. A seaworthy, watertight, floatable container for use in an offshore wind turbine maintenance program, said container being able to safely survive being disposed in the sea and protect maintenance people and cargo located in said container, said container including: at least one access door assembly for enabling cargo and at least one maintenance person to be loaded and unloaded from said container; a capsule attachment line holding-and-releasing apparatus for selectively holding and selectively releasing a capsule attachment line for selectively enabling said at least one container to be moved to or from a wind turbine tower; and a truncated outer shell defining the exterior of said container, said truncated outer shell having a nose portion, wherein said capsule attachment line discharge port is located in said nose portion. 